WO2013011901A1 - Method for separating/collecting rare earth element, and apparatus for separating/collecting rare earth element - Google Patents

Abstract

The purpose of the present invention is to provide: a separation/collection method which can increase the distribution ratio between different rare earth elements for the purpose of achieving the reduction of cost in the separation/collection of a rare earth element; and a separation/collection apparatus which can achieve the method. A method for separating/collecting a rare earth element according to the present invention is a method for separating/collecting a specific rare earth element from an aqueous solution containing ions of multiple rare earth elements, and comprises: an aggregation step of adding a water-soluble polymer having an acidic group to the aqueous solution and then adding a water-soluble polymer having an amino group to the resultant mixture in such a manner that the total number of the amino groups becomes greater than that of the acidic groups of the water-soluble polymer having the acidic group, thereby producing an aggregated product; a separation/collection step of separating and collecting the aggregated product from the aqueous solution; a dissolution step of dissolving the aggregated product in an acid, thereby producing a solution; and a re-aggregation step of adding a water-soluble polymer having an amino group to the solution, thereby producing a re-aggregated product.

Description

Separation and recovery method of rare earth element and separation and recovery device of rare earth element

The present invention relates to a method and apparatus for separating and recovering rare earth elements contained in a magnet alloy or the like.

Magnetic alloys (ferromagnetic alloys) used in motors of magnetic recording devices and hybrid vehicles etc. are added to iron as the main component, and small amounts of neodymium (Nd), dysprosium (Dy), etc. to increase the coercive force. Rare earth elements are added. In recent years, separation, recovery, and reuse of these rare earth elements from discarded magnetic alloys have been studied from the viewpoint of effective utilization of resources.

In addition to the above magnetic alloys, phosphors containing rare earth elements used in cathode ray tubes, plasma display panels (PDPs), etc. are also enormous amounts on a global scale, so separation of rare earth elements from these phosphors Recovery is also required.

Here, it is said that rare earth elements are difficult to separate as a single substance because various physical properties and chemical properties are similar to each other. For example, the electronegativity of rare earth elements is in the range of 0.86 to 1.14, in particular the electronegativity of Nd in the magnet alloy is 1.07 and that of Dy is very close to 1.10. Further, the ion radius of the rare earth element is also in the range of 0.0745 to 0.117 nm, and in particular, the ion radius of Nd in the magnet alloy is 0.099 nm, and that of Dy is close to 0.091 nm (both trivalent ions).

As a conventional method for separating rare earth elements such as Nd and Dy, there is a solvent extraction method. For example, in Non-Patent Document 1 (scientific article), when an alloy containing a plurality of rare earth elements is dissolved in a strong acid, a phosphoric acid-based extractant and a hydrocarbon-based organic solvent are added and stirred, and left standing It is described that different types of rare earth elements are distributed to water and an organic solvent depending on the type of extractant.

Patent Document 1 discloses a water-soluble polymer having an acidic group by adding a water-soluble polymer having an acidic group and a water-soluble polymer having an amino group to waste water in which a metal salt is dissolved. It is described that a water-soluble polymer having an amino group is crosslinked to trap metal ions in waste water and precipitate as an aggregate.

Unexamined-Japanese-Patent No. 2010-172815

However, since the solvent extraction method of Non Patent Literature 1 uses a hydrocarbon-based organic solvent, recovery and processing of the solvent in consideration of the load on the environment and health are required, which causes an increase in cost. In addition, since the distribution ratio of different types of rare earth elements is small in the solvent extraction method, it is necessary to repeat the solvent extraction process several dozen times to increase the purity of the separated rare earth elements (for example, to 99% or more). is there.

Moreover, the metal recovery method by aggregate precipitation of the above-mentioned Patent Document 1 is originally intended to efficiently recover (remove) metal ions from a large amount of industrial wastewater, and it is aggressive to separate for each metal species. Not for the purpose. That is, separation of different types of rare earth elements by element type is not sufficiently considered.

Therefore, an object of the present invention is a separation and recovery method capable of increasing the distribution ratio of different types of rare earth elements to solve the above problems and achieving cost reduction in separation and recovery of rare earth elements, and a separation and recovery apparatus for realizing the same. To provide.

(I) According to one aspect of the present invention, there is provided a method of separating and recovering a specific rare earth element from an aqueous solution containing ions of a plurality of rare earth elements, wherein a water-soluble polymer having an acidic group is added to the aqueous solution. And adding a water-soluble polymer having an amino group so that the total number of amino groups is larger than the total number of acidic groups of the water-soluble polymer having an acidic group, and forming an aggregate; Products are separated and recovered from the aqueous solution, a dissolving process of dissolving the aggregates with an acid to form a solution, and a water-soluble polymer having an amino group in the solution to form a reaggregate A rare earth element separation and recovery method comprising the steps of:

The present invention can add the following improvement or change in the rare earth element separation and recovery method (I) according to the present invention described above.
(I) When the total number of rare earth element ions having the smallest ion radius among the plurality of rare earth elements is “R”, and the total number of acid groups of the water-soluble polymer having the acid group is “C” The water-soluble polymer having the acid group is added to the aqueous solution so as to satisfy the inequality “R ≦ C ≦ 3R”.
(Ii) The water-soluble polymer having an acidic group has an average molecular weight of 126 to 25,000, and the water-soluble polymer having an amino group has an average molecular weight of 60 to 25,000.
(Iii) an aggregate washing step of washing the aggregates separated and recovered from the aqueous solution, and a water-soluble polymer having an acidic group after adding a water-soluble polymer having an acidic group to the aqueous solution from which the aggregates are separated A water-soluble polymer having an amino group is added such that the total number of amino groups is larger than the total number of acidic groups of the polymer, and the method further comprises the additional aggregation step of additionally forming an aggregate.
(Iv) The hydrogen ion exponent pH of the aqueous solution is 1 or more and 5 or less.
(V) The water-soluble polymer having an amino group is added such that the pH of the aqueous solution is 6 or more and 9 or less.
(Vi) Before adding the water-soluble polymer having an amino group in the reaggregation step, a strong base is added such that the pH of the solution in which the aggregate is dissolved is 1 or more and 3 or less.
(Vii) The water-soluble polymer having an amino group has a primary amino group and a tertiary amino group.
(Viii) A cation exchange resin having an acid group is added in place of the water-soluble polymer having an acid group in the aggregation step.
(Ix) The cation exchange resin contains magnetic powder.

(II) According to another aspect of the present invention, there is provided an apparatus for separating and recovering a specific rare earth element from an aqueous solution having ions of a plurality of types of rare earth elements, wherein a mixing tank and a mechanism for charging the aqueous solution into the mixing tank , A mechanism for adding a water-soluble polymer having an acidic group to the mixing tank, a mechanism for adding a water-soluble polymer having an amino group to the mixing tank, a mechanism for stirring the aqueous solution, and aggregation from the aqueous solution The rare earth element separation and recovery device is provided with a mechanism for separating and recovering a substance, and a mechanism for dissolving the aggregates and adding an acid for producing a solution to the mixing tank.

The present invention can add the following improvements and changes in the rare earth element separation and recovery apparatus (II) according to the present invention described above.
(X) The apparatus further comprises a mechanism for washing the aggregate separated and recovered from the aqueous solution.
(Xi) The mechanism for adding the water-soluble polymer having an acidic group to the mixing tank and the mechanism for adding the water-soluble polymer having an amino group to the mixing tank each have a plurality of discharge nozzles. .
(Xii) further comprising a mechanism for suctioning the aqueous solution after the aggregates are separated and collected.
(Xiii) A mechanism for adding a cation exchange resin to the mixing vessel instead of the mechanism for adding the water-soluble polymer having the acidic group to the mixing vessel, or further comprising a cation exchange resin in the mixing vessel It is housed.
(Xiv) The cation exchange resin has a magnetic powder, and is further provided with a mechanism for separating and collecting the cation exchange resin from the mixing tank by a magnetic separation method.
(Xv) A filter is provided at the bottom of the mixing tank to filter the aggregates.
(Xvi) The apparatus further includes a mechanism for disposing the upper surface of the filter at a position the same as or higher than the upper end of the inner wall of the mixing tank.
(Xvii) The filter comprises a mechanism for heating the aggregates.
(Xviii) The surface of the member in contact with the aggregates is treated to have a contact angle with water of 90 ° or more.

According to the present invention, it is possible to provide a separation and recovery method in which distribution ratios of different types of rare earth elements are enhanced, and a separation and recovery apparatus for realizing the same.

It is a schematic diagram explaining the aggregation process in the separation-and-recovery method concerning the present invention. It is a schematic diagram explaining the melt | dissolution process and reaggregation process in the separation-and-recovery method which concerns on this invention. In the separation-and-recovery method concerning the present invention, it is a mimetic diagram explaining the condensation process using a cation exchange resin. It is a schematic diagram explaining the flow of the process of the separation-and-recovery method concerning the present invention. It is a schematic diagram which shows one structure of the rare earth element separation-and-recovery apparatus which concerns on this invention. It is a schematic diagram which shows the operation | movement which collect | recovers reaggregates in the separation-and-recovery apparatus shown in FIG. It is a schematic diagram which shows another one structure of the rare earth element separation-and-recovery apparatus based on this invention. It is a schematic diagram which shows the further another structure of the rare earth element separation-and-recovery apparatus based on this invention. It is a schematic diagram which shows the further another structure of the rare earth element separation-and-recovery apparatus based on this invention. It is a schematic diagram which shows the further another structure of the rare earth element separation-and-recovery apparatus based on this invention. It is a schematic diagram which shows the mechanism which collect | recovers rare earth elements from an aggregate collection | recovery tank in the separation-and-recovery apparatus shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. However, the present invention is not limited to the embodiments described herein, and appropriate combinations and improvements can be made without departing from the technical concept of the invention.

In this specification, an aqueous solution in which Nd and Dy are mixed is described as an example of an aqueous solution in which a plurality of types of rare earth elements are mixed. This is because these two types of rare earth elements are widely used as magnet alloys in many types of motors. As mentioned above, the ion radius of Nd is slightly larger than that of Dy. In addition to Nd and Dy, for example, lanthanum (La), cerium (Ce), europium (Eu), terbium (Tb) or the like used in phosphors can be separated and recovered according to the same principle.

First Embodiment (Method for separating and recovering rare earth elements)
(1) Basic Procedure A method for separating and recovering Dy from an aqueous solution in which Nd ions and Dy ions are mixed will be described with reference to FIG. 1 and FIG. When the magnet alloy is dissolved in acid, Nd and Dy both become trivalent ions, so both Nd ions and Dy ions below mean trivalent ions unless otherwise specified.

(1-1) Aggregation Process FIG. 1 is a schematic view illustrating the aggregation process in the separation and recovery method according to the present invention. As shown in FIG. 1, first, a water-soluble polymer 4 having an acidic group is added to an aqueous solution in which Nd ions 1 and Dy ions 2 are mixed. Then, the Nd ion 1 and the Dy ion 2 form an ionic bond with the acidic group 3 of the water-soluble polymer 4.

Next, a water-soluble polymer 6 having an amino group is added. Then, the Nd ion 1 having a larger ion radius than the Dy ion 2 preferentially coordinates with the amino group 5 of the water-soluble polymer 6 having an amino group to form a water-soluble aggregate 7 (hereinafter referred to as an aggregate) In some cases, 7 is referred to as solution 7). On the other hand, the ionic bond between the acid group 3 of the water-soluble polymer 4 having an acid group and the amino group 5 of the water-soluble polymer 6 having an amino group results in intermolecular crosslinking to form an aggregate 8 insoluble in water. Do. When the aggregate 8 is formed, the Nd ion 1 and the Dy ion 2 not forming the water-soluble aggregate 7 are taken into the aggregate 8.

In the formation of the aggregate 8, one amino group 5 is ionically bonded to one acidic group 3. Therefore, considering the amount of amino group 5 necessary to form aggregate 7, the amino acid of water-soluble polymer 6 having an amino group is more than the total number of acidic groups 3 of water-soluble polymer 4 having an acidic group. The total number of groups 5 needs to be large.

There is a reason for the order of adding the water soluble polymers 4 and 6. If the water-soluble polymer 4 having an acid group is added after the water-soluble polymer 6 having an amino group is added, it is immediately associated with the water-soluble polymer 6 from the region to which the water-soluble polymer 4 is added. Because of aggregation, most of the Dy ions 2 dispersed throughout the aqueous solution are not taken into the aggregate and remain in the aqueous solution. Therefore, the water-soluble polymer 4 having an acid group is first added to capture the Dy ion 2, and then the water-soluble polymer 6 having an amino group is added. Thereby, the Dy ions 2 in the entire aqueous solution region in the reaction vessel can be taken into the aggregate 8.

(1-2) Separation and Recovery Step After forming the aggregate 8, the aggregate 8 is separated and recovered from the aqueous solution by filtration or the like.

(1-3) Aggregate Washing with Water Next, the separated and collected aggregate 8 is washed with water to remove the dissolved component adhering to the surface of the aggregate 8. It is preferable that the solution removed by washing is returned to the aqueous solution.

(1-4) Additional Agglomeration Step The dissolved component separated from the aggregate 8 also contains Dy. Therefore, after the water-soluble polymer 4 having an acidic group is added to the aqueous solution from which the aggregate 8 is separated, the water-soluble polymer 6 having an amino group is further added to form an aggregate additionally. Thereby, Dy can be recovered from the solution. In other words, it is possible to efficiently recover Dy without discarding it as much as possible.

Even when the aggregate is separated and recovered from a mixture liquid of rare earth elements other than Nd and Dy, the rare earth element having the smaller ion radius is preferentially taken into the aggregate 8, and the dissolved portion has the ion radius. The larger rare earth element will be predominantly present.

(1-5) Dissolution Step FIG. 2 is a schematic view illustrating a dissolution step and a reaggregation step in the separation and recovery method according to the present invention. When an acid having a stronger acidity than the acid group 3 of the water-soluble polymer 4 is brought into contact with the aggregate 8, the dissociated ion state of the acid group 3 of the water-soluble polymer 4 changes to a non-dissociated state. As a result, the ionic bond bridging the two polymers (water-soluble polymers 4 and 6) disappears, and the aggregate 8 dissolves. The acid dissociation constant pKa of the acid to be added is preferably small. In other words, the stronger the acidity is, the faster the dissolution of the aggregate 8 proceeds, so a strong acid (pKa <1, for example, hydrochloric acid etc.) is preferable.

By the way, the aggregate 8 is dissolved even if a base is added instead of the acid. When a base stronger in basicity than the amino group 5 of the water-soluble polymer 6 is brought into contact with the aggregate 8, a state in which the amino group 5 of the water-soluble polymer 6 having an amino group is not dissociated from the dissociated ionic state Change to As a result, the ionic bond bridging the two polymers (water-soluble polymers 4 and 6) disappears, and the aggregate 8 dissolves. However, when the hydrogen ion index pH is 8 or more, the Nd ion 1 and the Dy ion 2 change to hydroxides that are poorly soluble in water. As a result, although the aggregate 8 dissolves, hydroxides of Nd and Dy precipitate, causing problems in the next step. From this, it is preferable to carry out the dissolution process of dissolving the aggregate 8 by adding an acid.

(1-6) Reaggregation step After adding the base to the solution in which the aggregate 8 is dissolved in the dissolution step and adjusting the pH to about 2, the water-soluble polymer 6 having an amino group has a pH of about 5 to 5 When it is added until it reaches 6, reaggregates 8 'precipitate. Here, a water-soluble polymer 6 having an amino group may be added as a base for pH adjustment. However, if the liquid of Aggregate 8 is strongly acidic, it is necessary to add water-soluble polymer 6 having a vast amount of amino groups before adjusting pH to about 2, so adjust pH As a base, it is more preferable to use a strong base (base dissociation constant pKb <0, for example, sodium hydroxide etc.).

In this step, since the Nd ions 1 incorporated in the aggregate 8 formed in the aggregation step first form the association 7, the Nd ions in the dissociated state in the solution decrease, as a result, reaggregation The proportion of Dy ions 2 in the object 8 'is increased. That is, Dy can be separated and recovered from the aqueous solution in which Nd ions and Dy ions are mixed at a high distribution ratio.

(1-7) Roasting step The reaggregated substance 8 'having Dy concentrated is separated and recovered by filtration or the like and then roasted. Thereby, Dy ₂ O ₃ is obtained and becomes a recycled raw material. For example, the obtained rare earth oxide can be reduced and recycled to a rare earth magnet such as a hard disk drive (HDD).

(2) Basic Principle When a water-soluble polymer 6 having an amino group 5 is added to an aqueous solution in which Nd ions and Dy ions are mixed, a water-soluble polymer in which the Nd ion 1 preferentially has an amino group 5 The reason for combining with 6 is estimated as follows.

Since the trivalent Nd ion 1 has 3 electrons in the 4f orbit, 11 electrons are required to fill the orbit with electrons. On the other hand, since the number of electrons on the 4f orbital is nine, the trivalent Dy ion 2 requires five electrons to fill the orbital with electrons. Since the Nd ion 1 requires more electrons than the Dy ion 2 to satisfy the 4f orbital, it is presumed that the attractive force with the amino group 5 functioning as an electron donating group is larger. In other words, since the amino group 5 is more easily coordinated by the Nd ion 1, the Nd ion 1 is preferentially distributed in the solution 7, and the Nd ion 1 in a dissociated state in the solution decreases. As a result, the Dy ions 2 in the aggregate 8 and the recoagulate 8 'become relatively large.

If the trivalent ions of the rare earth element are arranged in ascending order of the number of electrons in the 4f orbital, it is as follows. Cerium ion (Ce ³⁺ , number of electrons on 4f orbital = 1), praseodymium ion (Pr ³⁺ , number of electrons on 4f orbital = 2), neodymium ion (Nd ³⁺ , number of electrons on 4f orbital = 3) , Promethium ion (Pm ³⁺ , number of electrons on 4f orbit = 4), samarium ion (Sm ^{3 +} , number of electrons on 4f orbit = 5), europium ion (Eu ³⁺ , number of electrons on 4f orbit = 6 ), Gadolium ion (Gd ³⁺ , number of electrons on 4f orbit = 7), terbium ion (Tb ³⁺ , number of electrons on 4f orbit = 8), dysprosium ion (Dy ³⁺ , number of electrons on 4f orbit = 9), holmium ion (Ho ³⁺ , number of electrons on 4f orbit = 10), erbium ion (Er ^{3 +} , number of electrons on 4f orbit = 11), thulium ion (Tm ^{3 +} , on 4f orbit) Electron number = 12), Ytterbium ion (Yb ³⁺ , electron number on 4f orbit = 13). Considering these trivalent ions of the rare earth element in terms of the ion radius, if the number of electrons on the 4f orbit increases, the ion radius decreases due to lanthanide contraction. The smaller the ion radius, the easier it is to be incorporated into the aggregate 8 or recoagulate 8 '. Further, as the ion radius is smaller (the number of insufficient electrons in the 4f orbital is smaller), coordination with the amino group 5 becomes more difficult. That is, the one having a small ion radius is distributed to the aggregate 8 and the recoagulate 8 ′, and the one having a large ion radius is distributed in the solution 7.

If the above aggregation step is performed using an aqueous solution in which trivalent ions of the above-mentioned rare earth elements are mixed in equivalent amounts, Yb ³⁺ is most easily taken into aggregate 8. The order of Tm ³⁺ , Er ³⁺ ,... Is as follows, and the more electrons on the 4f orbital, the easier it is to be taken into aggregate 8. On the other hand, Ce ³⁺ is the largest to be distributed to the dissolved component 7, and in the order of Pr ³⁺ , Nd ^3+,.

As mentioned above, the present invention aims to increase the distribution ratio of different types of rare earth elements. Here, “raising the distribution ratio of rare earth elements” in the present invention will be briefly described. In the prior art, the purpose is usually to separate and recover as much of the rare earth element as possible from the raw material containing the rare earth element (for example, the discarded rare earth magnet alloy). On the other hand, "to increase the distribution ratio of the rare earth elements" in the present invention means to increase the purity of the rare earth elements to be separated and collected (to separate and collect the rare earth elements having high purity). In this respect, the present invention differs from the prior art in basic concept.

In order to achieve the object of the present invention, it is a key point on the process to minimize the mixing of other types of rare earth elements into the aggregates containing the rare earth elements to be separated and collected. In other words, prior to incorporation and failure of the rare earth element to be separated and recovered into the aggregate, priority is given to suppressing the mixing of the other rare earth element into the aggregate. In the following, points for achieving the object of the present invention will be described in more detail.

(3) Polymeric material used (3-1) Water-soluble polymer having an acidic group As the acidic group 3 of the water-soluble polymer 4 having an acidic group 3, for example, a carboxyl group (—COOH) or a sulfonic acid group ( -SO ₃ H).

More specifically, as a water-soluble polymer having a carboxyl group, polyacrylic acid is preferable from the viewpoint of being inexpensive and being easy to form an ionic bond with an amino group. Besides these, polyaspartic acid and polyglutamic acid derived from amino acids are also suitable. Alginic acid is a type of main component of seaweed such as kelp, and has a feature that environmental load is small in that raw materials are derived from organisms.

Examples of the water-soluble polymer having a sulfonic acid group include polyvinyl sulfonic acid and polystyrene sulfonic acid. These sulfonic acid groups are preferable in that they have a higher acidity than carboxyl groups, so the proportion of forming ionic bonds with amino groups is high, and stable aggregates can be obtained.

In addition, when the water solubility of the polymer having an acid group is not sufficient, the water solubility (solubility in water) is improved by forming a part of the acid group with an ammonium salt structure, a sodium salt structure, and / or a potassium salt structure. It is possible to By adding a polymer in which some of the acidic groups have an ammonium salt structure, a sodium salt structure, and / or a potassium salt structure, it is possible to efficiently form an ionic bond with a water-soluble polymer having an amino group Become.

When the average molecular weight of the water-soluble polymer 4 having an acidic group 3 is too large, during aggregation, the type of element to be distributed to the dissolved component 7 is physically entangled with a long molecular chain (without association with the binding group) There is a tendency to be taken into aggregate 8 and reaggregate 8 'together. This tendency becomes remarkable when the average molecular weight of the water-soluble polymer 4 exceeds 25,000. Therefore, the average molecular weight of the water-soluble polymer 4 having the acidic group 3 is preferably 25,000 or less.

In addition, in the dissolution step of the formed aggregate, the smaller the average molecular weight of the water-soluble polymer 4 used, the easier it is to dissolve and the dissolution is in a shorter time. From this viewpoint, the average molecular weight of the water-soluble polymer 4 having the acidic group 3 is more preferably 7,000 or less, and still more preferably 5,000 or less. The shortening of the process time of the dissolution step is particularly advantageous when the aggregation step and the dissolution step are repeated a plurality of times. For example, a water-soluble polymer 6 having an amino group 5 (average molecular weight 25,000) is added to an aqueous solution in which a water-soluble polymer 4 having an acidic group 3 is dissolved to form an aggregate, thereby forming hydrochloric acid (1 N) When this aggregate was dissolved to use, the aggregate having an average molecular weight of 25,000 of the water-soluble polymer 4 used took about 1 minute to completely dissolve. The aggregate having an average molecular weight of 7,000 of the water-soluble polymer 4 used was completely dissolved in about 40 seconds. The aggregate having an average molecular weight of 5,000 of the water-soluble polymer 4 used was completely dissolved in about 3 seconds.

On the other hand, at least two or more acidic groups are required to form the aggregate 8 and the reaggregate 8 '. Among the organic compounds having two or more acidic groups, the one having the lowest molecular weight is oxalic acid, and the molecular weight is 126. Oxalic acid can also be considered as a polymer material having a repeating basic unit of “—COOH”. Therefore, the lower limit of the molecular weight of the water-soluble polymer 4 is 126.

In addition, in the aggregation step, as the average molecular weight of the water-soluble polymer 4 used is larger, intermolecular cross-linking with the water-soluble polymer 6 having the amino group 5 is more easily formed, and the poor solubility of the formed aggregate is increased. . That is, since the utilization rate of the added water-soluble polymer 4 is increased, the trapping efficiency of the rare earth element ion to be separated and collected is increased. For example, when the aggregation step of forming an aggregate by adding a water-soluble polymer 6 (average molecular weight 5,000) having an amino group 5 was carried out, the ratio of forming the insoluble aggregate among the added water-soluble polymer 4 Was about 90% when the average molecular weight of the water-soluble polymer 4 used was less than 1,000, and about 95% when the average molecular weight of the water-soluble polymer 4 used was 1,000 or more and less than 2,000. When the average molecular weight of the water-soluble polymer 4 was 2,000 or more, it was about 98%. From these results, the average molecular weight of the water-soluble polymer 4 is required to be at least 126, preferably 1,000 or more, and more preferably 2,000 or more.

(3-2) Cation Exchange Resin It is also possible to use a cation exchange resin instead of the water-soluble polymer having an acidic group described above. FIG. 3 is a schematic view illustrating an aggregation step using a cation exchange resin in the separation and recovery method according to the present invention. The cation exchange resin 9 to be used preferably has, for example, a sulfonic acid group or a carboxyl group as the acidic group 3. .

As shown in FIG. 3, when cation exchange resin 9 is added to an aqueous solution in which Nd ion 1 and Dy ion 2 are mixed, Nd ion 1 and Dy ion 2 are the acid groups 3 and ions of cation exchange resin 9 Join. Thereafter, when the water-soluble polymer 6 having the amino group 5 is further added, the Nd ion 1 preferentially forms an aggregate 7 with the water-soluble polymer 6 and dissolves. At the same time, the acidic groups 3 of the cation exchange resin 9 and the amino groups 5 of the water-soluble polymer 6 are ionically bonded while preferentially trapping the Dy ions 2. The relationship between the number of acidic groups 3 of the cation exchange resin 9 and the number of amino groups 5 of the water-soluble polymer 6 is the same as in the above-mentioned “(1-1) aggregation step”.

With regard to the size of the cation exchange resin 9, when the particle size of the cation exchange resin 9 is too large, the amount for trapping the rare earth element ion per unit mass decreases. On the other hand, if the particle size is too small, the filter and the like are easily clogged by filtration in the separation and recovery step. Therefore, the average particle diameter of the cation exchange resin 9 is preferably about 0.1 mm to 3 mm. In order to improve the trapping rate of the rare earth element ions, it is preferable to increase the surface area by providing asperities on the surface of the cation exchange resin 9 or the like.

Also, in the separation and recovery step, the cation exchange resin 9 used to trap rare earth element ions (bound to the surface) is separated from non-aggregates (dissolved 7) by filtration etc. It is preferable to be easy to do. In this case, the cation exchange resin 9 can also be regarded as an aggregate 8. When a metal having a large specific gravity is contained in the inside of the cation exchange resin 9, the specific gravity as the cation exchange resin 9 also becomes large, so that it becomes easy to precipitate. Further, by containing magnetic powder in the inside of the cation exchange resin 9, it can be collected magnetically and it becomes possible to utilize magnetic separation in the separation and recovery step.

(3-3) Water-soluble polymer having an amino group As the water-soluble polymer 6 having an amino group 5, polyethyleneimine is preferable in that the ratio of the amino group per unit mass is maximized. In addition, linear amino groups such as polyvinylamine and polyallylamine are also preferable because they are relatively inexpensive and easily dissolved in water. Although chitosan has a slightly lower solubility in water, it is obtained by hydrolyzing chitin, which is the main component of the exoskeleton of organisms (eg, crab, shrimp, beetles, cockroaches, etc.), so the raw material is said to be of biological origin. It has the feature that environmental load is small in point. Also suitable are amino acid-derived polylysine and polyarginine.

As described above, it is more efficient for the water-soluble polymer 6 having an amino group 5 to have as many amino groups as possible per unit mass. Specifically, a structure having a small repeating basic unit or a structure having as many amino groups as possible in the repeating basic unit is preferable. For example, polyethylenimine is efficient among water-soluble polymers 6 having an amino group 5 because the repeating basic unit is “—C ₂ H ₄ N” and the molecular weight is as small as about 43. In addition to this, some structures of polyallylamine may be mentioned. For example, it is the following compound.

Compound A has a molecular weight of the repeating basic unit of about 72. In compound B, a molecule having a molecular weight of about 72 and a molecule of about 100 are combined to form a repeating basic unit. Since the water-soluble polymer 6 having an amino group 5 other than these has a pyrrole skeleton, a sulfonyl moiety or the like, the molecular weight of the repeating basic unit is around 150 to 300. Among these, compounds A and B are preferable among polyethyleneimine and polyallylamine.

In addition, when the amino group 5 of the water-soluble polymer 6 is composed of a primary amino group and a tertiary amino group, it tends to form an aggregate 7 with the Nd ion 1 more easily than the Dy ion 2. Polyethyleneimine has all three types of primary amino group, secondary amino group, and tertiary amino group. The compound B also has two types of primary amino group and tertiary amino group. The use of these polyethyleneimines and polyallylamines in the separation and recovery method of the present invention is preferable in that the Dy ions 2 are selectively separated and recovered from an aqueous solution in which Nd ions 1 and Dy ions 2 are mixed.

The viscosity of the water-soluble polymer 6 having an amino group 5 increases as the average molecular weight increases, and thus handling becomes difficult from the viewpoint of input amount control and input operation. Specifically, when the average molecular weight of the water-soluble polymer 6 having an amino group 5 such as polyethylenimine or polyallylamine exceeds 100,000, the viscosity is 1,000 mPa · s at 20 ° C. even in an aqueous solution of 10 mass%. It becomes more than s. When the viscosity is 1,000 mPa · s or more, it is necessary to use a device with a small discharge amount per unit time (for example, a dispenser, etc.) in the operation of injecting the water-soluble polymer 6, and the separation and recovery operation is efficient. Operation becomes difficult. In order to operate the separation and recovery process efficiently, it is desirable that the viscosity of the water-soluble polymer 6 is low, so that the average molecular weight of the water-soluble polymer 6 having the amino group 5 is preferably at least 100,000 or less.

Further, as in the case of the water-soluble polymer 4, when the average molecular weight of the water-soluble polymer 6 having the amino group 5 is excessive, the element species to be distributed to the dissolved component 7 is physically separated by a long molecular chain There is a tendency to be entangled (without association with the linking group) together into aggregate 8 and reaggregate 8 '. This tendency becomes remarkable when the average molecular weight of the water-soluble polymer 6 exceeds 25,000. Therefore, the average molecular weight of the water-soluble polymer 6 having an amino group 5 is more preferably 25,000 or less.

In addition, as described above, in the dissolution step of the formed aggregate, the smaller the average molecular weight of the water-soluble polymer 6 used, the easier it is to dissolve and the dissolution is performed in a shorter time. From this viewpoint, the average molecular weight of the water-soluble polymer 6 having an amino group 5 is more preferably 7,000 or less, and most preferably 5,000 or less. For example, to an aqueous solution in which a water-soluble polymer 4 (average molecular weight 25,000) having an acidic group 3 is dissolved, a water-soluble polymer 6 having an amino group 5 is added to form an aggregate, and hydrochloric acid (1 N) When this aggregate was dissolved to use, the aggregate of water-soluble polymer 6 having an average molecular weight of 25,000 required about 1 minute to completely dissolve. The aggregate having an average molecular weight of 7,000 of the water-soluble polymer 6 used was completely dissolved in about 40 seconds. The aggregate having an average molecular weight of 5,000 of the water-soluble polymer 6 used was completely dissolved in about 3 seconds. The shortening of the process time of the dissolution step is particularly advantageous when the aggregation step and the dissolution step are repeated a plurality of times.

On the other hand, at least two or more amino groups are required to form aggregate 8 and reaggregate 8 '. The organic compound having two or more amino groups and having the lowest molecular weight is ethylenediamine, and the molecular weight is 60. Ethylenediamine can also be considered as a polymer material having a repeating basic unit of “—CH ₂ NH ₂ ”. Therefore, the lower limit of the molecular weight of the water-soluble polymer 6 is 60.

Further, as in the case of the water-soluble polymer 4 having an acidic group, in the aggregation step, as the average molecular weight of the water-soluble polymer 6 used is larger, the intermolecularity with the water-soluble polymer 4 having an acidic group 3 is Crosslinks are likely to be formed and the poor solubility of the resulting aggregates is increased. That is, since the utilization rate of the added water-soluble polymer 6 is increased, the trapping efficiency of the rare earth element ions to be separated and recovered is increased. For example, when a flocculation step of forming an aggregate by adding a water-soluble polymer 4 (average molecular weight 5,000) having an acidic group 3 is performed, a ratio of forming an insoluble aggregate among the added water-soluble polymer 6 Was about 90% when the average molecular weight of the water-soluble polymer 6 used was less than 1,000, and about 95% when the average molecular weight of the water-soluble polymer 6 used was 1,000 or more and less than 2,000. When the average molecular weight of the water-soluble polymer 6 was 2,000 or more, it was about 98%. From these results, the average molecular weight of the water-soluble polymer 6 needs to be at least 60, preferably 1,000 or more, and more preferably 2,000 or more.

(4) Addition Ratio of Water-Soluble Polymer According to the separation and recovery method of the present invention, the rare earth element ion having the smallest ion radius among the plural kinds of rare earth element ions present in the aqueous solution is the aggregate 8 and the reaggregates 8 'It is taken in preferentially. At this time, it is important to prevent other types of rare earth element ions from being incorporated into the aggregate as much as possible, and in order to realize it, the addition ratio of the water-soluble polymer is an important process factor.

First, the addition amount of the water-soluble polymer 4 having the acidic group 3 is the total number (R) of the rare earth element ion having the smallest ion radius (ie, the rare earth element ion to be separated and recovered). Or more) (R C C). When “C <R”, the total number of acid groups is too small, and the recovery rate of rare earth element ions to be separated and recovered decreases. The total number R of rare earth element ions can be estimated, for example, by an inductively coupled plasma method.

In water, since the rare earth ion is trivalent and the acid group 3 is monovalent, a maximum of three ionic bonds are formed per one rare earth ion. Here, if all of the rare earth element ions in the aqueous solution are the rare earth element ions to be separated and collected, the total number C of the acidic groups 3 should be at least 3 times the total number R of the rare earth element ions to be separated and collected. If 3R ≦ C), the rare earth element ion in the aqueous solution is in principle 100% trapped in the aggregate.

However, since the mixed aqueous solution targeted by the present invention contains plural kinds of rare earth element ions, the total number C of the acidic groups 3 is more than three times the total number R of the rare earth element ions to be separated and recovered ( If 3R <C) or more than 3R, it will also trap rare earth element ions other than the rare earth elements to be separated and collected. That is, the separation ability of the rare earth element species (distribution ratio of the rare earth element) is lowered. From this, it is desirable that the total number C of the acidic groups 3 is three times or less (C ≦ 3R) of the total number R of rare earth element ions (the rare earth element ions having the smallest ion radius) to be separated and collected.

From the above viewpoint, the addition amount of the water-soluble polymer 4 having the acidic group 3 desirably satisfies the inequality “R ≦ C ≦ 3R”. The total number C of the acidic groups 3 is more preferably 2.5 times or less (C ≦ 2.5 R) the total number R of rare earth element ions to be separated and recovered from the viewpoint of minimizing the mixing of other types of rare earth elements. It is more desirable that the ratio be 2 times or less (C.ltoreq.2R).

On the other hand, when using a cation exchange resin 9 having an acidic group 3 instead of the water-soluble polymer 4 having an acidic group 3, the cation exchange resin 9 is acidic because the cation exchange resin 9 itself is solid. It is harder to move than the water-soluble polymer 4 having the group 3 (no fluidity like the water-soluble polymer 4). Therefore, in order to increase the probability of association with the rare earth element ion to be captured, it is necessary to increase the addition amount of the cation exchange resin 9 compared to the water-soluble polymer 4 having the acidic group 3. Specifically, in the case of using the cation exchange resin 9 having an acidic group 3, the total number of acidic groups 3 is about 3 to 10 times the total number of acidic groups 3 of the water-soluble polymer 4. Is preferred.

By performing the aggregation step and the additional aggregation step under the conditions as described above, the distribution ratio of the rare earth element can be increased.

(5) Acid and Base Used (5-1) Acid In the dissolution step, a common acid can be used as the acid used for dissolving the aggregate 8. The linear water-soluble polymer 6 having the amino group 5 constituting the aggregate 8 forms a salt structure with the amino group 5 and the added acid by addition of an acid, thereby forming the aggregate 8 The aggregate 8 dissolves because the ionic bond is eliminated. When an acid (weak acid) having a low acidity is used, a large amount of addition is required to dissolve the aggregate 8, so the acid used is a strong acid (pKa <1), particularly strong inorganic acid (eg hydrochloric acid, sulfuric acid) , Nitric acid) is preferred. In addition, when an acid having a carboxyl group or a sulfonic acid group is used as the acid to be used for dissolution, these acid groups adversely affect the additional aggregation step in the next step, so acids (water-soluble polymer 4 having these acid groups) Acid having the same acid group 3) is not preferred.

(5-2) Base In the reaggregation step, a common base can be used as a base used to form reaggregate 8 ′ from the solution in which aggregate 8 is dissolved. However, since a strong acid is used in the previous dissolution step, the use of only a weak base causes a buffering action. Therefore, it is preferable to use a strong base (pKb <0) as the base added to adjust the pH of the solution in which the aggregate 8 is dissolved to about 2. Specifically, strong inorganic bases (for example, sodium hydroxide, potassium hydroxide and the like) are preferable. Thereafter, the water-soluble polymer 6 having an amino group 5 is further added to form a reaggregate 8 '. In addition, if there is no special restriction | limiting in the amount of bases to add, you may add only the water-soluble polymer 6 which has the amino group 5, and you may perform a reaggregation process.

(6) Scheme for improving separation and recovery rate A method for improving separation and recovery rate of a predetermined rare earth element in the separation and recovery method according to the present invention (Dy ions from an aqueous solution in which Nd ions and Dy ions are mixed The method of selectively incorporating into aggregates) will be described in more detail using FIG. FIG. 4 is a schematic view illustrating the flow of steps of the separation and recovery method according to the present invention.

(A) Stirring Step First, as shown in FIG. 4A, the mixed aqueous solution 10 in which Nd ions and Dy ions are mixed is introduced into a mixing tank 12 having a shuttered filter 11 at the bottom. The stirring mechanism 13 is operated to stir the mixed aqueous solution 10 in the mixing tank 12.

(B) Agglomeration Step While stirring the mixed aqueous solution 10 in the mixing tank 12, the water-soluble polymer 4 having an acidic group is added, and then the water-soluble polymer 6 having an amino group is added. Then, as shown in (b) of FIG. 4, aggregates 8 are formed in the mixing tank 12.

The formation of the aggregate 8 inhibits the flow of the water-soluble polymer 6 having an amino group, and if the aggregate that should be originally formed in the mixing tank 12 remains unformed, the recovery rate of separation of Dy may be reduced. There is sex. Therefore, in order to cause aggregation to occur in the entire mixed aqueous solution 10 in the mixing tank 12, the mechanism for adding the water-soluble polymer 6 having an amino group comprises a plurality of nozzles for releasing the water-soluble polymer 6, It is preferable to make the agglutination reaction occur in the entire region of the mixing tank 12.

(C) Rinsing Step Next, by releasing the shutter of the shuttered filter 11 disposed at the bottom of the mixing tank 12, the dissolved portion 7 of the mixed aqueous solution 10 is discharged out of the mixing tank 12, as shown in FIG. The state is as shown in (c). Thereafter, the remaining aggregate 8 is washed with water 14 to remove the dissolved matter 7 attached to the aggregate 8.

(D) Dissolution step of aggregate Next, when the shutter of the shuttered filter 11 is closed and the aqueous solution 15 of acid is dropped to the aggregate 8, the aggregate 8 is dissolved.

(E) Reaggregation Step Next, as shown in (d) of FIG. 4, an aqueous solution 16 of a base is added to the solution in which the aggregate 8 is dissolved, and the pH of the solution is adjusted to 1 to 5. Thereafter, a water-soluble polymer 6 having an amino group is added until the pH of the solution reaches 6-9. Then, as shown in (e) of FIG. 4, the dissolved matter 7 and the reagglomerated substance 8 ′ are formed in the mixing tank 12.

Next, the shutter 7 of the filter with shutter 11 disposed at the bottom of the mixing tank 12 is opened to discharge the dissolved portion 7 out of the mixing tank 12, and the state as shown in FIG. 4C is obtained. Here, by repeating the steps (c) to (e), Nd ions are mainly removed from the rare earth element ions trapped in the aggregates 8 and the reaggregates 8 ′, and as a result, the Dy ions are removed. The percentage of Moreover, the separation and recovery rate of Dy can be further improved by collecting the dissolved portion 7 and repeating the additional aggregation step, the dissolution step and the re-aggregation step.

(F) Final water washing step When the Dy ions are increased to the desired distribution ratio, the shutter of the shuttered filter 11 disposed at the bottom of the mixing tank 12 is opened as shown in (f) of FIG. The part 7 is drained out of the mixing tank 12 and the remaining reaggregates 8 'are finally washed with water 14.

(G) Agglomerate heating step The final washed reaggregate 8 'is heated in the air. As a result, the used flocculant (water-soluble polymer 4 and water-soluble polymer 6, or cation exchange resin 9 and water-soluble polymer 6) is thermally decomposed, and the Dy ion combines with oxygen to form Dy ₂ O ₃ Is obtained (see (g) in FIG. 4). When the obtained rare earth element oxide is recycled to a magnetic alloy, it can be reduced to Dy and then used as a magnet of a motor of an HDD or a hybrid car.

Second embodiment (separating and collecting apparatus for rare earth elements)
(7) Form 1 of separation and recovery apparatus
Next, an embodiment of the rare earth element separation and recovery apparatus according to the present invention will be described with reference to FIGS. 5 and 6. Here, a case where Dy ions are selectively separated and recovered from a mixed aqueous solution in which Nd ions and Dy ions are mixed as rare earth element ions will be described as an example.

FIG. 5 is a schematic view showing one configuration of the rare earth element separation and recovery apparatus according to the present invention. The pH of the mixed aqueous solution (an aqueous solution in which Nd ions and Dy ions are mixed) to be introduced into the separation and recovery apparatus shown in FIG. 5 is preferably 1 or more and 5 or less. As an example, the pH of the mixed aqueous solution is 3.0. If the pH of the mixed aqueous solution to be added is less than 1, the acidity is too high, and even if a water-soluble polymer having an amino group is added in a later step, it becomes difficult to form aggregates, so the recovery rate of separation of Dy ions decreases. Do. On the other hand, when the pH of the mixed aqueous solution to be added exceeds 5, when the water-soluble polymer having an amino group is added in a later step, the pH of the mixed aqueous solution becomes too high, and some of the formed aggregates are re-reacted. It dissolves to lower the separation and recovery of Dy ions.

First, a mixed aqueous solution (an aqueous solution containing Nd ions and Dy ions) is introduced into the mixing tank 17 through the mixed aqueous solution pipe 19 by the mixed aqueous solution supply pump 18. Thereafter, the mixed aqueous solution in the mixing tank 17 is stirred by the overhead stirrer 21 equipped with the stirring blade 20. Stirring of the mixed aqueous solution is continued until aggregates 28 are formed in a later step.

Next, an aqueous solution of a water-soluble polymer having an acidic group is introduced into the mixing tank 17 from the first tank 22 through the first pipe 24 by the first pump 23.

Next, an aqueous solution of a water-soluble polymer having an amino group is introduced into the mixing tank 17 from the second tank 25 through the second pipe 27 by the second pump 26. Then, the water-soluble polymer having an amino group and the water-soluble polymer having an acidic group are associated in the mixing tank 17 to form an aggregate 28. After the formation of aggregates 28, the stirring is stopped. The amount of the water-soluble polymer having an amino group is adjusted so that the pH of the aqueous solution in the mixing tank 17 is 6 or more and 9 or less.

Subsequently, when the shutter 29 is opened, the liquid (dissolution) other than the aggregate 8 is discharged from the mixing tank 17 through the filter 30. Since the aggregate 8 is blocked by the filter 30, it is not discharged from the mixing tank 17. After the liquid component of the mixing tank 17 is discharged, the shutter 29 is closed. The discharged solution passes through a valve 31 and enters a recovery tank 32 disposed below the mixing tank 17.

Next, deionized water is dropped by the third pump 34 from the third tank 33 through the third pipe 35 onto the aggregates 28 remaining in the mixing tank 17. This operation is intended to remove the Nd component adhering to the surface of the aggregate 28. When the deionized water is partially accumulated in the mixing tank 17, the shutter 29 is opened to discharge the deionized water, and then the shutter 29 is closed. By repeating the steps of pouring the deionized water and discharging the deionized water several times, most of the Nd components adhering to the surface of the aggregate 28 are removed.

Next, an acid (for example, a hydrochloric acid aqueous solution) is introduced into the mixing tank 17 from the fourth tank 36 through the fourth pipe 38 by the fourth pump 37 to dissolve the aggregates 28. When the aggregate 28 starts to dissolve, it is gently stirred by the overhead stirrer 21. In this state, an aqueous solution of hydrochloric acid is added until the aggregate 28 is completely dissolved.

When the aggregate 28 is completely dissolved, the fifth pump 40 feeds the base (for example, aqueous sodium hydroxide solution) into the mixing tank 17 from the fifth tank 39 through the fifth pipe 41. The addition of the sodium hydroxide aqueous solution is continued until the pH of the aqueous solution in the mixing tank 17 becomes 1 to 3.

Thereafter, an aqueous solution of a water-soluble polymer having an amino group is introduced into the mixing tank 17 from the second tank 25 through the second pipe 27 by the second pump 26. In addition, the input amount of the water-soluble polymer having an amino group is adjusted such that the pH of the aqueous solution in the mixing tank 17 is 6 or more and 9 or less. This step produces reaggregates.

Next, as described above, the shutter 29 is opened to discharge the liquid (dissolved matter) other than the reagglomerated material from the mixing tank 17. Thereafter, washing the reaggregation with deionized water, adding an aqueous solution of hydrochloric acid to dissolve the reaggregation, adding sodium hydroxide aqueous solution and a water-soluble polymer having an amino group to form a reaggregation Repeat several times. As a result, the proportion of Nd ions in the reagglomerate decreases, and as a result, the proportion of Dy ions increases (ie, the purity of the Dy component increases).

After raising the percentage of Dy ions in the reagglomerate to the desired value, the reagglomerate is dried and collected. In order to dry the aggregates / reaggregates, the filter 30 preferably includes a heating mechanism (not shown).

FIG. 6 is a schematic view showing an operation of recovering reaggregated material in the separation and recovery apparatus shown in FIG. As shown in FIG. 6, the bottom 17 'of the mixing tank is configured to be slidable in the vertical direction in the figure with respect to the inner wall 42 of the mixing tank. The bottom 17 'of the mixing vessel is raised together with the shutter 29 and the filter 30, so that the top of the shutter 29 or filter 30 is at the same or slightly higher than the upper end of the inner wall 42 of the mixing vessel. Next, the reaggregates 28 'on the shutter 29 and / or the filter 30 are collected by a scraper or the like. By doing so, the reaggregated matter 28 'can be recovered easily and without waste. Thereafter, the bottom 17 'of the mixing tank is lowered to return to the original state. As a matter of course, the positional relationship between the bottom 17 'of the mixing tank and the inner wall 42 of the mixing tank is relative, and the operation of FIG. 6 is performed by lowering the inner wall 42 of the mixing tank. It is also good.

Next, the reaggregated material recovered above is heated in the air. As a result, the organic compound component (water-soluble polymer having an acidic group, water-soluble polymer having an amino group) in the reagglomerate is decomposed and removed, and the Dy ion combines with oxygen to form Dy ₂ O _3. can get.

Since the aqueous solution (the dissolved component) collected in the collection tank 32 also contains the Dy component, the dissolved component collected in the collection tank 32 is put into the mixing tank 17, and the additional aggregation step, the dissolution step, and the reaggregation described above are performed. Dy can be recovered from the solution by repeating the steps. This can further improve the separation and recovery rate of Dy as a whole.

Further, separating and recovering Dy from the aqueous solution stored in the recovery tank 32 leads to an increase in the proportion of Nd ions in the aqueous solution (dissolved matter) recovered in the recovery tank 32. Therefore, when the proportion of Nd ions increases to a desired value, Nd ₂ O ₃ can be recovered by heating the aqueous solution (dissolved matter) to remove water and organic compound components.

When aggregates are formed in the aggregation step and re-aggregation step, their size may be too small and it may take a long time to settle down the mixing tank. In that case, the suspension in the mixing tank may be transferred to a centrifuge tube and centrifuged to separate the aggregate and the dissolved component.

In addition, since aggregation occurs instantaneously when a water-soluble polymer having an amino group is added in the aggregation step and reaggregation step, if the aqueous solution is not sufficiently stirred, unreacted amino acid in the aggregates or recoagulates A water-soluble polymer having a group may be incorporated, and the rare earth element ion to be trapped may be dropped. Therefore, it is preferable that the tip of the pipe to which the water-soluble polymer having an amino group is added has a plurality of discharge nozzles so that the water-soluble polymer to be charged can be easily dispersed in the aqueous solution.

The stirring blade 20 of the overhead stirrer 21, the mixing tank 17, the fourth tank 36 containing an aqueous solution of acid, and the fourth pipe 38 may be corroded because they touch strong acids such as hydrochloric acid. . Therefore, it is preferable to form an acid resistant resin film for preventing direct contact of the acid with these members. Specifically, a paint obtained by dissolving a thermoplastic resin such as a polycarbonate resin or an acrylic resin in an organic solvent such as acetone or 2-butanone is applied to a desired portion of the above-described member, and the organic solvent is evaporated to evaporate the organic solvent. It is possible to form a resin film.

In addition, a coating obtained by dissolving an epoxy resin or a phenol resin and a curing agent (for example, diamine) in an organic solvent is applied to a desired portion of the above member and then heated to thermally cure resin molecules. It is possible to form an acid resistant resin film. A resin composed of a combination of an epoxy resin or a phenol resin and a curing agent is particularly suitable when the member is made of metal (for example, SUS, aluminum, etc.) because the adhesion to metal is high. Of course, the above-mentioned member may be made of a highly acid resistant resin.

If the aggregates 28 or reaggregates 28 'stick to the inner wall 42 of the mixing tank, the surface of the shutter 29 or the surface of the filter 30, the recovery of the aggregates 28 / reaggregates 28' may be disturbed. Therefore, it is desirable that the surface of the member to which the aggregates 28 / reaggregates 28 'may come in contact be treated so as to lower the surface energy.

As a surface with low surface energy, for example, it is preferable that the contact angle with water be 90 ° or more. This is because the formed aggregate 28 / reaggregate 28 'contains a large amount of water, so that the aggregate 28 / reaggregate 28' is also less likely to adhere to the surface that is likely to repel water. The treatment for lowering the surface energy is not particularly limited as long as the contact angle with water on the surface of the resin film is 90 ° or more, but as one example, the compatibility with the above-mentioned acid resistant resin is high and A resin film is formed by mixing and applying a highly water-repellent material (for example, a silicone compound having a siloxane skeleton in the molecular structure, a fluorine compound having a large number of fluorine atoms in the molecular structure, etc.) to the above-mentioned paint There is a way.

The present inventors add various organic compounds to the above-mentioned acid resistant resin film (polycarbonate resin, acrylic resin, epoxy resin cured with curing agent, phenol resin cured with curing agent), and the water repellency effect thereby (Surface energy reduction effect) was investigated. As a result, acid-resistant resin films formed by adding 2 to 5% by mass of the following organic compounds C to M with respect to the resin in the paint have high contact angles with water as high as 100 ° or more, and aggregates There was an effect that the adhesion of was hardly found visually. This was a significant difference compared to the case of a resin film whose contact angle with water was less than 90 °. Specifically, the added organic compounds C to M are as follows.

The fluorine-containing chain in the molecular structure of the above compound is called a perfluoropolyether chain, and good results were obtained when the average molecular weight of the perfluoropolyether chain was 1,500 or more and 3,000 or less in any of the compounds. When the average molecular weight of the perfluoropolyether chain was less than 1,500, the water repellency was not sufficient. In addition, when the average molecular weight is more than 3000, the compatibility with the acid resistant resin is low, and it is easily separated in the paint, so that it is difficult to form a homogeneous resin film.

(8) Form 2 of separation and recovery device
Next, another embodiment of the rare earth element separation and recovery apparatus according to the present invention will be described with reference to FIG. FIG. 7 is a schematic view showing another configuration of the rare earth element separation and recovery apparatus according to the present invention. As shown in FIG. 7, in the present embodiment, no shuttered filter is disposed in the lower region of the mixing tank.

In the same manner as in the first embodiment, first, a mixed aqueous solution (an aqueous solution containing Nd ions and Dy ions) prepared separately is passed through the mixed aqueous solution pipe 19 by the mixed aqueous solution supply pump 18 and a filter with a shutter in the lower region Into a mixing tank 43 not equipped with

Next, while the aqueous solution in the mixing tank 43 is well stirred by the overhead stirrer 21, the aqueous solution of the water-soluble polymer having an acidic group is passed from the first tank 22 through the first pipe 24 by the first pump 23. Charge into mixing vessel 43. Thereafter, an aqueous solution of a water-soluble polymer having an amino group is introduced into the mixing tank 43 from the second tank 25 through the second pipe 27 by the second pump 26 to form the aggregates 28.

Next, the dissolved component in the mixing tank 43 is transferred from the mixing tank 43 to the collecting tank 32 by the dissolved liquid recovery pump 44 through the dissolving pipe 45. At that time, since the filter 46 is provided at the water intake port of the dissolution pipe 45, it is possible to suppress the mixture of the aggregates 28 in the recovery tank 32.

The other device configurations and steps are the same as in the first embodiment. The separation and recovery apparatus of the present embodiment is characterized in that since the dissolved component is sucked by a pump, the aggregate and the dissolved component can be separated in a shorter time as compared with the above-described separation and recovery apparatus of the first embodiment.

(9) Form 3 of separation and recovery device
Next, another embodiment of the rare earth element separation and recovery apparatus according to the present invention will be described with reference to FIG. FIG. 8 is a schematic view showing still another configuration of the rare earth element separation and recovery apparatus according to the present invention. As shown in FIG. 8, in the present embodiment, the shuttered filter is not disposed in the lower region of the mixing tank, and the mixing tank has a mechanism for causing the solution to flow out from the side wall.

As in the first embodiment, first, a mixed aqueous solution (an aqueous solution containing Nd ions and Dy ions) prepared separately is introduced into the mixing tank 49 through the mixed aqueous solution pipe 19 by the mixed aqueous solution supply pump 18. The mixing tank 49 is not provided with a shuttered filter in the lower region, and is provided with a discharge port 48 having a valve 47 for controlling the flow rate of the solution on the side wall.

Next, while the aqueous solution in the mixing tank 49 is well stirred by the overhead stirrer 21, the aqueous solution of the water-soluble polymer having an acidic group is passed from the first tank 22 through the first pipe 24 by the first pump 23. Charge into mixing tank 49. Thereafter, an aqueous solution of a water-soluble polymer having an amino group is introduced into the mixing tank 49 from the second tank 25 through the second pipe 27 by the second pump 26 to form the aggregates 28.

Next, the valve 47 of the discharge port 48 is opened to discharge the dissolved component from the mixing tank 49 to the recovery tank 32. At that time, it is desirable to provide a filter (not shown) at the tip of the discharge port 48 and / or the water intake port, whereby the inclusion of the aggregates 28 in the recovery tank 32 can be suppressed. Further, the discharge port 48 preferably includes a mechanism (not shown) capable of moving in the vertical direction of the mixing tank 49. Thereby, it is possible to more efficiently separate the aggregate and the solution. The other device configurations and steps are the same as in the first embodiment.

(10) Form 4 of separation and recovery device
Next, another embodiment of the rare earth element separation and recovery apparatus according to the present invention will be described with reference to FIG. FIG. 9 is a schematic view showing still another configuration of the rare earth element separation and recovery apparatus according to the present invention. As shown in FIG. 9, this embodiment basically has the same apparatus configuration as that of the above-mentioned embodiment 1, but instead of using a water-soluble polymer having an acidic group, a cation exchange resin is used to form a rare earth element. They differ in that they are separated and recovered. Specifically, there is no mechanism (a first tank, a first pump, a first pipe) for charging an aqueous solution of a water-soluble polymer having an acidic group into the mixing tank, and the cation in the mixing tank 17 in advance. Insert the replacement resin 50.

First, a separately prepared mixed aqueous solution (an aqueous solution containing Nd ions and Dy ions) is introduced into the mixing tank 17 through the mixed aqueous solution pipe 19 by the mixed aqueous solution supply pump 18. Thereafter, the aqueous solution in the mixing tank 17 is stirred by the overhead stirrer 21.

Next, an aqueous solution of a water-soluble polymer having an amino group is introduced into the mixing tank 17 from the second tank 25 through the second pipe 27 by the second pump 26. Then, the water-soluble polymer having an amino group and the acid group of the cation exchange resin 50 are ionically bonded in the mixing tank 17 to form an aggregate on the surface of the cation exchange resin 50. Stirring is stopped after the formation of aggregates.

Next, the shutter 29 is opened to discharge the solution from the mixing tank 17. The cation exchange resin 50 in which the aggregates are formed on the surface is blocked by the filter 30, so it is not discharged from the mixing tank 17. After the dissolved content of the mixing tank 17 is discharged, the shutter 29 is closed. The discharged solution passes through a valve 31 and enters a recovery tank 32 disposed below the mixing tank 17.

Next, deionized water is allowed to fall on the cation exchange resin 50 remaining in the mixing tank 17 from the third tank 33 through the third pipe 35 by the third pump 34, and the surface of the cation exchange resin 50 Wash. After draining the washing water, the fourth pump 37 feeds the hydrochloric acid aqueous solution from the fourth tank 36 through the fourth pipe 38 into the mixing tank 17 to collect the aggregates on the surface of the cation exchange resin 50. Let it dissolve.

Next, the aqueous solution of sodium hydroxide is introduced into the mixing tank 17 through the fifth tank 39 through the fifth pipe 41 by the fifth pump 40 to adjust the pH of the solution, and the second pump 26 subsequently When an aqueous solution of a water-soluble polymer having an amino group is introduced into the mixing tank 17 from the tank 25 of the No. 2 through the second pipe 27, reaggregates are formed on the surface of the cation exchange resin 50.

By repeating the formation of aggregates on the surface of the cation exchange resin 50, the washing of the aggregates, the dissolution of the aggregates, and the re-formation of the aggregates, the Nd ions are mainly removed from the aggregates and the Dy ions are removed. The proportion will increase.

After raising the percentage of Dy ions in the reagglomerate to the desired value, the reagglomerate is dissolved in aqueous hydrochloric acid. The shutter 29 is opened to discharge the dissolved liquid (other than the cation exchange resin 50) from the mixing tank 17. The discharged liquid portion is recovered through the valve 31 to the second recovery tank 51 disposed below the mixing tank 17. Furthermore, the surface of the cation exchange resin 50 is washed with deionized water, and the washing solution is also transferred to the second recovery tank 51.

Next, the sodium hydroxide aqueous solution is introduced into the second recovery tank 51 through the fifth tank 39 through the fifth pipe 41, the mixing tank 17, and the valve 31 by the fifth pump 40, and the second recovery is performed. The pH of the aqueous solution in the tank 51 is adjusted to around 2 (for example, 1 to 3). Subsequently, when an aqueous solution of a water-soluble polymer having an amino group is added from the sixth tank 52 through the sixth pipe 54 by the sixth pump 53, reaggregates 55 are formed.

Next, when the shutter 56 is opened, the liquid (dissolved matter) other than the reaggregate 55 is discharged from the second recovery tank 51 through the filter 57. After the liquid component in the second recovery tank 51 is discharged, the shutter 56 is closed, and the reagglomerated material 55 is heated and dried.

Thereafter, the dried reaggregates 55 on the filter 57 are collected by a scraper or the like. At this time, similarly to FIG. 6, the bottom of the second recovery tank 51 is raised with respect to the inner wall of the second recovery tank 51 together with the shutter 56 and the filter 57 for recovery, or the second recovery tank 51 is It is preferable to lower the inner wall relative to the bottom of the second recovery tank 51 for recovery.

Next, the recovered reaggregation 55 is heated in the air to decompose and remove the organic compound component (water-soluble polymer having an acidic group, water-soluble polymer having an amino group) in the reaggregation 55 , Dy ₂ O ₃ are obtained.

In the separation and recovery apparatus of this embodiment, the aggregates in the mixing tank 17 are formed by adhering to the cation exchange resin 50 by using the cation exchange resin 50. The size of the aggregates can be increased more than that. Therefore, when the aggregate and the solution are separated by filtration, the filter 30 is less likely to be clogged, and the filter 30 can be more easily separated (for example, in a short time).

After the solution is recovered in the second recovery tank 51, when an alkali metal hydroxide (for example, sodium hydroxide, potassium hydroxide, etc.) is added, it is combined with the Dy ion and poorly soluble in water. It produces dysprosium. The rare earth element can also be recycled by filtering this compound out and reducing it.

(11) Form 5 of separation and recovery device
Next, still another embodiment of the rare earth element separation and recovery apparatus according to the present invention will be described with reference to FIG. FIG. 10 is a schematic view showing still another configuration of the rare earth element separation and recovery apparatus according to the present invention. As shown in FIG. 10, this embodiment basically has the same apparatus configuration as the above-mentioned embodiment 4, but in that the separation and recovery of the rare earth elements are performed using the magnetic separation method instead of the filtration by the filter. It is different. More specifically, the cation exchange resin 58 placed in the mixing tank 17 contains magnetic powder inside. In addition, in FIG. 10, illustration of the part which overlaps with FIG. 9 is partially omitted from a viewpoint of simplification of drawing.

As in the above-mentioned embodiment 4, first, a separately prepared mixed aqueous solution (an aqueous solution containing Nd ions and Dy ions) is introduced into the mixing tank 17, and then an aqueous solution of a water-soluble polymer having an amino group is mixed. By charging into the tank 17, aggregates are formed on the surface of the magnetic powder-containing cation exchange resin 58.

Next, the shutter 29 is opened to discharge the dissolved component from the mixing tank 17 and the surface of the magnetic powder-containing cation exchange resin 58 is washed with deionized water, and then a hydrochloric acid aqueous solution is introduced into the mixing tank 17 to contain magnetic powder. The aggregates on the surface of the cation exchange resin 58 are dissolved. Next, a sodium hydroxide aqueous solution is introduced into the mixing tank 17 to adjust the pH of the solution, and subsequently, a water-soluble polymer having an amino group from the second tank 25 through the second pipe 27 by the second pump 26 The aqueous solution is placed in the mixing tank 17 to form reaggregates on the surface of the magnetic powder-containing cation exchange resin 58.

By repeating the formation of aggregates on the surface of the magnetic powder-containing cation exchange resin 58, the washing of the aggregates, the dissolution of the aggregates, and the re-formation of the aggregates, mainly Nd ions are removed from the aggregates, The percentage of Dy ions increases.

After the proportion of Dy ions in the reaggregates is increased to a desired value, the magnetic powder-containing cation exchange resin 58 having reaggregates formed on the surface is separated from the mixing tank 17 by the mechanism of separating and recovering by the magnetic separation method. Separate and collect.

A mechanism (magnetic powder-containing aggregate conveyance mechanism) for separating and collecting by the magnetic separation method includes a first roller 59, a second roller 60, a third roller 61, a fourth roller 62, and a conveyance belt 63. ing. The surface of the conveyance belt 63 between the fourth roller 62 and the first roller 59 to the second roller 60 has a magnetic force, whereby the magnetic powder-containing cation exchange resin in the mixing tank 17 is obtained. 58 can be adhered to the surface of the conveyor belt 63 along with the reaggregates. The surface of the conveyance belt 63 between the second roller 60, the third roller 61, and the fourth roller 62 has a structure having no magnetic force, and the reaggregates are formed from the surface of the conveyance belt 63. It falls off and falls into the aggregate collection tank 64. A shutter 65 and a filter 66 are provided at the lower part of the aggregate recovery tank 64.

In this way, the separation and recovery apparatus of the present embodiment can recover the magnetic powder-containing cation exchange resin 58 to which the reaggregated matter in which the Dy ions are trapped adheres from the mixing tank 17 to the aggregate recovery tank 64.

Next, with reference to FIG. 11, the process of recovering the rare earth element from the reaggregation formed on the surface of the magnetic powder-containing cation exchange resin 58 will be described. FIG. 11 is a schematic view showing a mechanism for recovering the rare earth element from the aggregate recovery tank in the separation and recovery apparatus shown in FIG.

As shown in FIG. 11, the seventh pump 68 feeds the hydrochloric acid aqueous solution to the aggregate recovery tank 64 from the seventh tank 67 through the seventh pipe 69, and the magnetic powder-containing cation exchange resin 58 Dissolve surface aggregates. Next, when the shutter 65 is opened, the liquid in which the aggregates are dissolved and the dissolved magnetic powder pass through the filter 66 and enter the collection tank 70. Meanwhile, the cation exchange resin remains on the filter 66. A shutter 74 and a filter 75 are provided at the lower part of the recovery tank 70.

Next, the eighth tank 72 feeds the sodium hydroxide aqueous solution into the recovery tank 70 through the eighth tank 71 and the eighth pipe 73. Then, the dissolved rare earth element precipitates as a poorly soluble hydroxide in water. Thereafter, when the shutter 74 is opened, the liquid (dissolved magnetic powder) passes through the filter 75 and enters the medicine recovery tank 76. On the other hand, the precipitated rare earth element hydroxide 77 remains on the filter 75. The rare earth element can be reused by recovering and reducing the hydroxide 77 of the rare earth element.

Hereinafter, the present invention will be described in more detail by way of specific examples. However, the following examples show specific examples of the contents of the present invention, and the present invention is not limited to these examples. Furthermore, the present invention is capable of various changes and modifications by those skilled in the art within the scope of the technical idea disclosed herein.

A mixed aqueous solution was prepared in which neodymium chloride (NdCl ₃ ) and dysprosium chloride (DyCl ₃ ) were dissolved in water. At that time, both Nd concentration and Dy concentration were adjusted to 5000 ppm. When the specific gravity of the obtained mixed aqueous solution is approximated to 1.0, the molar concentration of Nd and the molar concentration of Dy are 34.66 mmol / L and 30.77 mmol / L, respectively.

While putting 100 g of this mixed aqueous solution (rare earth element ion number is 6.54 mmol) in the mixing tank of the separation and recovery apparatus shown in FIG. 5 and stirring, a 10 mass% aqueous solution of polyacrylic acid as a water-soluble polymer having an acidic group 0.942 g (average molecular weight 5,000, repeat unit number 1.31 mmol) was added. Furthermore, 4.709 g (number of repeating units: 6.54 mmol) of a 10% by mass aqueous solution of Compound A was added as a water-soluble polymer having an amino group.

Then, white aggregates were formed. The resulting aggregate was filtered off with a filter and the aggregate on the filter was washed with deionized water. The aggregate was dissolved with hydrochloric acid, and the ratio of Nd and Dy in the aggregate was measured by inductively coupled plasma method to be about 20% and about 80%, respectively. In addition, when it was measured in the solution, it was found that Nd was about 3900 ppm and Dy was about 600 ppm. That is, the filtrate and the washing solution mainly contained Nd ions, and the aggregates mainly contained Dy ions. From this result, it was found that in the first aggregation step, about 88% by mass of Dy ions and about 22% by mass of Nd ions of the rare earth elements in the mixed solution were incorporated into the aggregate.

Next, the step of dissolving the aggregates and the step of reaggregation will be described more specifically.

When 1 N hydrochloric acid (HCl) aqueous solution was dropped to the aggregates, the aggregates gradually dissolved. While stirring this solution, a 1 N aqueous solution of sodium hydroxide (NaOH) was added dropwise until the pH reached about 2. While stirring this solution, a 10% by weight aqueous solution of Compound A was subsequently added dropwise until the pH reached about 8. Then, aggregates were formed again. The resulting reagglomerate was filtered off with a filter and the reaggregate on the filter was washed with deionized water.

The above is the dissolving and re-flocculating steps of the aggregate. By repeating these steps, the Nd ions in the aggregate gradually transfer to the filtrate, and as a result, the percentage of Dy ions in the aggregate increases.

The second time aggregation process (first time of the re-aggregation step), and Dy ions from about 77.4 wt% of the mixed aqueous solution of NdCl ₃ and DyCl ₃ charged into the mixing tank (≒ 0.88 ^2), about 4.8 wt% ( ≒ 0.222 ² ) Nd ions are incorporated into the aggregate. That is, the proportion (that is, the purity) of the Dy ion to the rare earth element ion in the aggregate is 94.2%.

About 68.15 mass% (≒ 0.88 ³ ) of Dy ions and about 1.06 mass% (≒ 0.88 ³ ) in the mixed aqueous solution of NdCl ₃ and DyCl ₃ charged into the mixing tank in the third aggregation step (second reaggregation step) ≒ 0.223 ³ ) Nd ions are incorporated into the aggregate. That is, the ratio (purity) of the Dy ion to the rare earth element ion in the aggregate is 98%.

After the concentration of Dy ions in the aggregate was increased to the desired ratio in this way, the aggregate was dissolved in 1 N aqueous hydrochloric acid solution, and then 5 N aqueous sodium hydroxide solution was added little by little while stirring. . Then, an aggregate was formed in the vicinity of neutrality, but the aggregate was dissolved by subsequently adding a 5 N aqueous solution of sodium hydroxide. When 5 N aqueous sodium hydroxide solution was further added, poorly soluble dysprosium hydroxide (Dy (OH) ₃ ) in water was precipitated. The precipitated dysprosium hydroxide was separated by filtration and recovered, and was reduced to obtain dysprosium alone.

The same steps as in Example 1 were performed until the desired proportion of Dy ions in the aggregate was obtained. After this, the aggregate was recovered in the step shown in FIG. When the recovered aggregate was heated, the organic compounds (water-soluble polymer having an amino group and water-soluble polymer having an acidic group) in the aggregate were thermally decomposed to form dysprosium oxide. When the obtained dysprosium oxide was reduced, dysprosium alone could be obtained.

Instead of using 0.942 g of a 10% by weight aqueous solution of polyacrylic acid (the number of repeating units is 1.31 mmol), 0.446 g (the number of acid groups) of a cation exchange resin having an exchange equivalent of 4.7 mEq / mL The same experiment as in Example 1 was conducted using 2.62 mmol) and using the separation and recovery apparatus shown in FIG.

100 g of the same mixed aqueous solution as in Example 1 (number of rare earth element ions: 6.54 mmol) was introduced into a mixing tank containing a cation exchange resin, and an aqueous solution of Compound A was added, resulting in the surface of the cation exchange resin. Aggregates were deposited. The aggregate was washed with deionized water, and then the step of dissolving and reaggregating the aggregate was repeated to increase the percentage of Dy ions in the aggregate.

After the concentration of Dy ions in the aggregate was increased to the desired proportion, the aggregate was dissolved with 1 N hydrochloric acid, and then dysprosium hydroxide was precipitated by adding an aqueous 5 N sodium hydroxide solution. The precipitated dysprosium hydroxide was separated by filtration and recovered, and was reduced to obtain dysprosium alone.

In addition, it was found through Example 3 that about 80% of Dy ions and about 20% of Nd ions are trapped in the aggregate in one aggregation step.

The separation and recovery of the rare earth element was performed in the same manner as in Example 3 using the separation and recovery apparatus of FIG. 10 and using a cation exchange resin containing magnetic powder inside the resin instead of a simple cation exchange resin. . By the same process as described above, the ratio of Dy ions in the aggregates formed on the surface of the magnetic powder-containing cation exchange resin was increased to a desired value. Thereafter, the magnetic powder-containing cation exchange resin to which the aggregates are attached was recovered by a recovery mechanism comprising a roller and a magnetic belt as shown in FIG.

The aggregate formed on the surface of the recovered magnetic powder-containing cation exchange resin was dissolved with hydrochloric acid in the same manner as in Example 1. Thereafter, an aqueous solution of sodium hydroxide was added to precipitate dysprosium hydroxide. The precipitated dysprosium hydroxide was separated by filtration and recovered, and was reduced to obtain dysprosium alone.

As a water-soluble polymer having an amino group, 5.625 g (number of repeating units: 3.27 mmol) of a 10% by weight aqueous solution of compound B was added instead of the compound A (10% by weight aqueous solution, 4.709 g). Separately, the rare earth element was separated and recovered in the same manner as in Example 1 except for the above. Since Compound B has two amino groups in the repeating units, the number of repeating units to be added is half of that of Compound A and the number of amino groups is the same.

When this compound B was used, it was found that about 85% by mass of Dy ions and about 20% by mass of Nd ions of the rare earth elements in the solution were incorporated into the aggregate by one aggregation step.

According to this example, it was confirmed that the ratio of Dy ions in the aggregate can be increased even when Compound B is used as a water-soluble polymer having an amino group.

As a water-soluble polymer having an amino group, 2.812 g (average molecular weight is 300, the number of amino groups is 6.54 mmol) of a 10% by weight aqueous solution of polyethyleneimine is added instead of the compound A (10% by weight aqueous solution, 4.709 g). Separately, the rare earth element was separated and recovered in the same manner as in Example 1 except for the above.

When this compound was used, it was found that about 83% by mass of Dy ions and about 21% by mass of Nd ions of the rare earth elements in the solution were incorporated into the aggregate by one aggregation step.

According to this example, it was confirmed that the ratio of Dy ions in the aggregate can be increased even if polyethylene imine is used as the water-soluble polymer having an amino group.

Instead of using 0.942 g of a 10% by weight aqueous solution of polyacrylic acid (average molecular weight is 5,000, the number of repeating units is 1.31 mmol) as a water-soluble polymer having an acidic group, 2.69 g of 10% by weight aqueous solution of polystyrene sulfonic acid (average molecular weight is 100,000, repeating unit number 1.31 mmol) was added. The separation and recovery of the rare earth elements were performed in the same manner as in Example 1 except for the above.

When this compound was used, it was found that about 86% by mass of Dy ions and about 21% by mass of Nd ions of the rare earth elements in the solution were incorporated into the aggregate by one aggregation step.

According to this example, it was confirmed that the ratio of Dy ions in the aggregate can be increased even if polystyrene sulfonic acid is used as the water-soluble polymer having an acidic group.

Instead of mixing the aqueous solution and dysprosium chloride neodymium chloride were dissolved in water, a cerium chloride (CeCl ₃₎ and ytterbium chloride (YbCl ₃₎ using a mixed aqueous solution prepared by dissolving in water. Separately, the rare earth element was separated and recovered in the same manner as in Example 1 except for the above. The Ce concentration and the Yb concentration in the mixed water solution were both adjusted to 5000 ppm.

In the case of a mixed aqueous solution of Ce ions and Yb ions, approximately 88% by mass of Yb ions and approximately 19% by mass of Ce ions of rare earth elements in the solution are incorporated into aggregates in one aggregation step. There was found. As described above, the Yb ion has 13 electrons in the 4f orbital, and the Ce ion has 1 electron. As a result of the experiment, it was found that Yb ions having a smaller ion radius (the number of electrons in the 4f orbital) are more easily trapped in the aggregate, and the ratio of Yb ions in the aggregate can be increased.

According to this example, it was confirmed that even the rare earth elements other than Nd and Dy are more easily trapped in the aggregate as the rare earth element having a smaller ion radius, and the ratio in the aggregate can be increased.

1 ... Nd ion, 2 ... Dy ion, 3 ... acidic group, 4 ... water soluble polymer having an acidic group, 5 ... amino group, 6 ... water soluble polymer having an amino group, 7 ... aggregate, dissolved matter, 8: aggregate, 8 ': reaggregate, 9: cation exchange resin, 10: mixed aqueous solution, 11: filter with shutter, 12: mixing tank, 13: stirring mechanism, 14: water, aqueous solution of 15: acid, DESCRIPTION OF SYMBOLS 16 aqueous solution of a base, 17 ... mixing tank, 17 '... bottom part of mixing tank, 18 ... mixed aqueous solution supply pump, 19 ... mixed aqueous solution piping, 20 ... stirring blade, 21 ... overhead stirrer, 22 ... 1st tank, 23 ... 1st pump, 24 ... 1st piping, 25 ... 2nd tank, 26 ... 2nd pump, 27 ... 2nd piping, 28 ... aggregates, 28 '... reaggregates, 29 ... shutters, Reference Signs List 30 filter, 31 valve, 32 recovery tank 33 third tank 34 third pump 35 third piping 36 fourth tank 37 fourth pump 38 ... 4th piping, 39 ... 5th tank, 40 ... 5th pump, 41 ... 5th piping, 42 ... inner wall of mixing tank, 43 ... mixing tank, 44 ... solution recovery pump, 45 ... solution Piping, 46: filter, 47: valve, 48: outlet, 49: mixing tank, 50: cation exchange resin, 51: second recovery tank, 52: sixth tank, 53: sixth pump, 54 ... sixth pipe, 55 ... reaggregates, 56 ... shutter, 57 ... filter, 58 ... magnetic powder containing cation exchange resin, 59 ... first roller, 60 ... second roller, 61 ... third roller , 62: fourth roller, 63: conveyance belt, 64: aggregate collection tank, 65: shutter, 66: filter, 67: seventh tank, 68: seventh pump, 69: seventh piping, 70 ... Recovery tank, 71: Eighth tank, 72: Eighth pump, 73: Eighth pipe, 74: Shutter, 75: Filter, 76: Drug recovery tank, 77: Hydroxide of rare earth element.

Claims (20)

1. A method of separating and recovering a specific rare earth element from an aqueous solution containing ions of a plurality of rare earth elements,
   After the water-soluble polymer having an acidic group is added to the aqueous solution, the water-soluble polymer having an amino group is added such that the total number of amino groups is larger than the total number of acidic groups of the water-soluble polymer having the acidic group. Flocculation step to form agglomerates,
   A separation and recovery step of separating and collecting the aggregates from the aqueous solution;
   Dissolving the aggregates with acid to form a solution;
   And a reaggregation step of adding a water-soluble polymer having an amino group to the solution to form a reaggregate.
2. In the rare earth element separation and recovery method according to claim 1,
   When the total number of the rare earth element ions having the smallest ion radius among the plurality of rare earth elements is “R” and the total number of acidic groups of the water-soluble polymer having the acidic group is “C”, the inequality formula “R 2. A method for separating and recovering rare earth elements, which comprises adding a water-soluble polymer having an acidic group to the aqueous solution so as to satisfy ≦ C ≦ 3R.
3. In the rare earth element separation and recovery method according to claim 1 or 2,
   The water-soluble polymer having the acidic group has an average molecular weight of 126 or more and 25,000 or less,
   The rare earth element separation and recovery method, wherein the average molecular weight of the water-soluble polymer having an amino group is 60 or more and 25,000 or less.
4. In the rare earth element separation and recovery method according to any one of claims 1 to 3,
   An aggregate water washing step of washing the aggregates separated and recovered from the aqueous solution;
   After adding a water-soluble polymer having an acidic group to the aqueous solution from which the aggregate has been separated, it has an amino group such that the total number of amino groups is larger than the total number of acidic groups of the water-soluble polymer having the acidic group A method of separating and recovering rare earth elements, the method further comprising the step of adding a water-soluble polymer and additionally forming an aggregate.
5. In the rare earth element separation and recovery method according to any one of claims 1 to 4,
   The method for separating and recovering rare earth elements, wherein a pH value of a hydrogen ion index of the aqueous solution is 1 or more and 5 or less.
6. In the rare earth element separation and recovery method according to any one of claims 1 to 5,
   A method of separating and recovering a rare earth element, comprising adding the water-soluble polymer having an amino group such that the pH value of the aqueous solution is 6 or more and 9 or less.
7. In the rare earth element separation and recovery method according to any one of claims 1 to 6,
   Before adding the water-soluble polymer having an amino group in the reaggregation step, a strong base is added so that the pH value of the solution in which the aggregates are dissolved is 1 or more and 3 or less. Rare earth element separation and recovery method.
8. In the rare earth element separation and recovery method according to any one of claims 1 to 7,
   A method of separating and recovering rare earth elements, wherein the water-soluble polymer having an amino group has a primary amino group and a tertiary amino group.
9. In the rare earth element separation and recovery method according to claim 1,
   A method for separating and recovering a rare earth element, which comprises adding a cation exchange resin having an acidic group in place of the water-soluble polymer having an acidic group in the aggregation step.
10. In the rare earth element separation and recovery method according to claim 9,
    The said cation exchange resin contains magnetic powder, The rare earth element separation-and-recovery method characterized by the above-mentioned.
11. An apparatus for separating and recovering a specific rare earth element from an aqueous solution having ions of a plurality of rare earth elements,
    Mixing tank,
    A mechanism for charging the aqueous solution into the mixing tank;
    A mechanism for adding a water-soluble polymer having an acidic group to the mixing tank;
    A mechanism for adding a water-soluble polymer having an amino group to the mixing tank;
    A mechanism for stirring the aqueous solution;
    A mechanism for separating and collecting aggregates from the aqueous solution;
    A rare earth element separation and recovery device comprising: a mechanism for dissolving the aggregates and adding an acid that generates a solution to the mixing tank.
12. In the rare earth element separation and recovery apparatus according to claim 11,
    A rare earth element separation and recovery apparatus, further comprising a mechanism for washing the aggregate separated and recovered from the aqueous solution.
13. In the rare earth element separation and recovery apparatus according to claim 11 or 12,
    The mechanism for adding the water-soluble polymer having the acidic group to the mixing tank and the mechanism for adding the water-soluble polymer having the amino group to the mixing tank include a plurality of discharge nozzles. And rare earth element separation and recovery equipment.
14. In the rare earth element separation and recovery apparatus according to any one of claims 11 to 13,
    A rare earth element separation and recovery apparatus, further comprising a mechanism for suctioning the aqueous solution after separation and recovery of the aggregates.
15. In the rare earth element separation and recovery apparatus according to claim 11 or 12,
    Instead of adding a water-soluble polymer having an acidic group to the mixing tank, a mechanism for adding a cation exchange resin to the mixing tank is further provided, or a cation exchange resin is contained in the mixing tank A rare earth element separation and recovery device characterized by
16. In the rare earth element separation and recovery apparatus according to claim 15,
    The rare earth element separation and recovery device according to claim 1, wherein the cation exchange resin has a magnetic powder and further comprises a mechanism for separating and recovering the cation exchange resin from the mixing tank by a magnetic separation method.
17. In the rare earth element separation and recovery apparatus according to claim 11 or 12,
    The rare earth element separation and recovery device according to claim 1, further comprising: a filter for filtering the aggregates at a lower portion of the mixing tank.
18. In the rare earth element separation and recovery apparatus according to claim 17,
    A rare earth element separation and recovery apparatus, further comprising a mechanism for disposing the upper surface of the filter at the same position as or higher than the upper end of the inner wall of the mixing tank.
19. In the rare earth element separation and recovery apparatus according to claim 17 or 18,
    The rare earth element separation and recovery apparatus, wherein the filter comprises a mechanism for heating the aggregates.
20. In the rare earth element separation and recovery apparatus according to any one of claims 11 to 19,
    The rare earth element separation and recovery apparatus is characterized in that the surface of the member in contact with the aggregate is treated so as to have a contact angle with water of 90 ° or more.

Images