JP7589482B2 - Adsorbent particles, packed column, and method for recovering rare earth elements - Google Patents

Description

The present invention relates to adsorbent particles, a packed column, and a method for recovering rare earth elements.

As an adsorbent that selectively adsorbs and desorbs rare earth elements, various particles have been proposed that have diglycolic acid introduced onto their surfaces (Patent Document 1, Non-Patent Documents 1 and 2).

Patent No. 6103611

Takeshi Ogata,Hydrometallurgy,152 (2015) 178-182 Tomohiro Shinozaki, Ind. Eng.Chem. Res., 57 (2018) 11424-11430

One aspect of the present invention provides adsorbent particles that have a high adsorption capacity for rare earth elements.

One aspect of the present invention relates to an adsorbent particle comprising a carrier particle containing an organic polymer containing a monomer unit derived from a styrene-based monomer, an organic compound having a functional group containing a sulfur atom and an amino group attached to the surface of the carrier particle, and a diglycolic acid residue bonded to the amino group. The content of sulfur atoms in the adsorbent particle is 0.5% by mass or more based on the mass of the adsorbent particle.

Another aspect of the present invention relates to a packed column comprising a column body and the above-mentioned adsorbent particles packed in the column body.

Yet another aspect of the present invention relates to a method for recovering rare earth elements, comprising contacting the adsorbent particles with a solution containing a rare earth element, thereby adsorbing the rare earth element onto the adsorbent particles, and contacting the adsorbent particles with an acidic solution containing an acid, thereby desorbing the rare earth element from the adsorbent particles.

According to one aspect of the present invention, it is possible to provide adsorbent particles that can adsorb a large amount of rare earth elements.

FIG. 1 is a schematic diagram illustrating one embodiment of a packed column.

Several embodiments of the present invention are described in detail below. However, the present invention is not limited to the following embodiments.

The adsorbent particles according to one embodiment include carrier particles containing an organic polymer, an organic compound having a functional group containing a sulfur atom and an amino group attached to the surface of the carrier particles, and a diglycolic acid residue bonded to the amino group.

The carrier particles are polymer particles containing an organic polymer as a main component. The organic polymer may be crosslinked. The proportion of the organic polymer in the carrier particles may be 50 to 100% by mass, 60 to 100% by mass, 70 to 100% by mass, 80 to 100% by mass, or 90 to 100% by mass.

The organic polymer forming the carrier particles according to one embodiment is a polymer containing monomer units derived from a styrene-based monomer (hereinafter sometimes referred to as a "styrene-based polymer"). The styrene-based monomer is styrene or a styrene derivative, and can be a crosslinkable monomer, a monofunctional monomer, or a combination thereof, as described below. The proportion of the styrene-based monomer in the styrene-based polymer can be 20 to 85 mol %, or 35 to 70 mol %, based on the total amount of monomer units constituting the styrene-based polymer.

The organic polymer may be a polymer containing a crosslinkable monomer as a monomer unit. The crosslinkable monomer may be, for example, a divinyl compound such as divinylbenzene, divinylbiphenyl, divinylnaphthalene, and divinylphenanthrene. These crosslinkable monomers may be used alone or in combination of two or more types. From the viewpoint of durability, acid resistance, and alkali resistance, the crosslinkable monomer may be divinylbenzene, which is a styrene-based monomer. The proportion of monomer units derived from the crosslinkable monomer in the organic polymer may be 1 to 80 mol%, 1 to 60 mol%, or 1 to 40 mol% based on the total amount of monomer units constituting the organic polymer.

The organic polymer may be a copolymer of a crosslinkable monomer and a monofunctional monomer. Examples of monofunctional monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-t-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene. These may be used alone or in combination of two or more. From the viewpoint of acid resistance and alkali resistance, the monofunctional monomer may be styrene.

The organic polymer may contain, as a monomer unit, a monomer having a reactive group that reacts with an organic compound described below, or may be a copolymer containing, as a monomer unit, a crosslinkable monomer and a monomer having a reactive group. The reactive group may be, for example, an epoxy group, a chloro group, or a combination thereof. An example of a monomer having an epoxy group is glycidyl methacrylate. An example of a monomer having a chloro group is 4-chloromethylstyrene. The proportion of monomer units derived from monomers having a reactive group in the organic polymer may be 15 to 80 mol %, or 30 to 65 mol %, based on the total amount of monomer units constituting the organic polymer.

The average particle size of the carrier particles may be 50 to 1000 μm, or 200 to 1000 μm. If the average particle size of the carrier particles is small, the pressure of the packed column packed with the adsorbent particles may increase. Here, the average particle size of the carrier particles can be determined by the following measurement method.
1) Particles are dispersed in water (containing a dispersant such as a surfactant) to prepare a dispersion containing 1% by mass of particles.
2) Using a flow-type particle image analyzer, the average particle size is measured from images of approximately 10,000 particles in the dispersion.

The carrier particles may be porous polymer particles. In the case of porous polymer particles, the surface inside the pores is also included in the "surface of the carrier particles". In the case of porous polymer particles, the specific surface area may be 50 m ² /g or more and 1000 m ² /g or less. The larger the specific surface area, the larger the amount of substance adsorbed tends to be. The specific surface area here means the BET specific surface area by adsorption of nitrogen gas.

The organic compound according to this embodiment has a functional group containing a sulfur atom. It is believed that the functional group containing a sulfur atom of the organic compound in the adsorbent particle interacts with the rare earth element, thereby further improving the adsorption amount of the rare earth element. Examples of the functional group containing a sulfur atom include a sulfonyl group (-S(=O) _2- ) and a sulfinyl group (-S(=O)-).

By introducing an organic compound having a functional group containing a sulfur atom, adsorbent particles containing sulfur atoms are formed. In particular, the content of sulfur atoms in the adsorbent particles may be 0.5 mass% or more, based on the mass of the adsorbent particles, and may be 20 mass% or less. If the content of sulfur atoms is large, the effect of improving the adsorption amount of rare earth elements tends to be greater. If the content of sulfur atoms is small, the adsorbent particles tend to be less likely to swell. Adsorbent particles that are less likely to swell can be packed into a column more efficiently. From the same viewpoint, the content of sulfur atoms may be 1.0 mass% or more, 2.0 mass% or more, 3.0 mass% or more, or 3.5 mass% or more based on the mass of the adsorbent particles, and may be 20 mass% or less, 19 mass% or less, 18 mass% or less, 17 mass% or less, 16 mass% or less, 15 mass% or less, 14 mass% or less, 13 mass% or less, 12 mass% or less, 11 mass% or less, 10 mass% or less, 9.0 mass% or less, 8.0 mass% or less, 7.0 mass% or less, 6.0 mass% or less, 5.0 mass% or less, or 4.0 mass% or less. Here, the content of sulfur atoms in the adsorbent particles may be a value measured by analysis of the adsorbent particles by combustion ion chromatography.

The organic compound further has an amino group. Some or all of the amino groups in the organic compound may form salts such as hydrochlorides and acetates. In the organic compound, a glycolic acid residue is bonded to the amino group. By combining an amino group with a functional group containing a sulfur atom, it is possible to obtain adsorbent particles with a larger adsorption amount of rare earth elements. In addition, in the adsorbent particles, it is also required to suppress the adsorption amount of metals other than rare earth elements. Examples of metals other than rare earth elements include iron. In the adsorbent particles according to this embodiment, by including an organic compound having an amino group and a functional group containing a sulfur atom, it is possible to increase the adsorption amount of rare earth elements while suppressing the adsorption of other metals such as iron.

The content of nitrogen atoms in the adsorbent particles may be 0.2% by mass or more based on the mass of the adsorbent particles. When the content of nitrogen atoms is large, the amount of adsorption of rare earth elements tends to be further improved. From the same viewpoint, the content of nitrogen atoms may be 0.5% by mass or more, 1.0% by mass or more, 1.5% by mass or more, 2.0% by mass or more, or 2.3% by mass or more based on the mass of the adsorbent particles. The upper limit of the content of nitrogen atoms is not particularly limited, but the content of nitrogen atoms may be, for example, 8.0% by mass or less, 7.0% by mass or less, 6.0% by mass or less, 5.0% by mass or less, 4.0% by mass or less, or 3.0% by mass or less based on the mass of the adsorbent particles. Here, the content of sulfur atoms in the adsorbent particles can be a value measured by elemental analysis using a combustion method for the adsorbent particles.

式（１）中、Ｒ^１はアルキレン基又は単結合を表し、Ｒ^２はアルキル基又は水素原子を表す。

In one embodiment, the organic compound having a functional group containing a sulfur atom and an amino group may be a polymer having a main chain containing a constitutional unit represented by the following formula (1) and a constitutional unit represented by the following formula (2).

In formula (1), R ¹ represents an alkylene group or a single bond, and R ² represents an alkyl group or a hydrogen atom.

In formula (1), when R ¹ is an alkylene group, the number of carbon atoms of the alkylene group may be 1 or more or 2 or more, and from the viewpoint of increasing the amount of adsorption of rare earth elements and further suppressing the amount of adsorption of metals other than rare earth elements, may be 4 or less, 3 or less, or 2 or less. When ^{R 2} is an alkyl group, the number of carbon atoms of the alkyl group may be 1 or more or 2 or more, and from the viewpoint of increasing the amount of adsorption of rare earth elements and further suppressing the amount of adsorption of metals other than rare earth elements, may be 4 or less or 3 or less.

When the organic compound is the above-mentioned polymer, the total content of the structural unit represented by formula (1) and the structural unit represented by formula (2) may be 20% by mass or more, 40% by mass or more, or 80% by mass or more, based on the total amount of structural units constituting the polymer, and may be 100% by mass or less, 80% by mass or less, or 40% by mass or less.

式（１１）中、Ｒ^１及びＲ^２は、前記式（１）におけるＲ^１及びＲ^２と同義である。 Such an organic compound may be, for example, a polymer having a main chain containing a constitutional unit represented by the following formula (11).

In formula (11), R ¹ and R ² have the same meanings as R ¹ and R ² in formula (1).

When the organic compound is a polymer having a main chain containing a structural unit represented by formula (11), the content of the structural unit represented by formula (11) may be 20% by mass or more, 40% by mass or more, or 80% by mass or more, based on the total amount of structural units constituting the polymer, and may be 100% by mass or less, 80% by mass or less, or 40% by mass or less.

式（３）中、ｍ及びｎはそれぞれ独立に正の整数を表す。 In another embodiment, the organic compound may be a polymer having a main chain including a constitutional unit represented by the following formula (3) and a constitutional unit represented by the above formula (2). The embodiment of the constitutional unit represented by formula (2) is as described above.

In formula (3), m and n each independently represent a positive integer.

In formula (3), m may be 1 or more, 2 or more, or 3 or more, and may be 3 or less, or 2 or less. In formula (3), n may be 1 or more, 2 or more, or 3 or more, and may be 3 or less, or 2 or less.

When the organic compound is the above-mentioned polymer, the total content of the structural unit represented by formula (3) and the structural unit represented by formula (2) may be 20% by mass or more, 40% by mass or more, or 80% by mass or more, based on the total amount of structural units constituting the polymer, and may be 100% by mass or less, 80% by mass or less, or 40% by mass or less.

Such an organic compound may be, for example, a polymer having a main chain containing a constitutional unit represented by the following formula (12): The polymer having a main chain containing a constitutional unit represented by the formula (12) may be a copolymer of diallylamine and sulfur dioxide.

When the organic compound is a polymer having a main chain containing a structural unit represented by formula (12), the content of the structural unit represented by formula (12) may be 20% by mass or more, 40% by mass or more, or 80% by mass or more, based on the total amount of structural units constituting the polymer, and may be 100% by mass or less, 80% by mass or less, or 40% by mass or less.

The above-mentioned polymer may further contain other structural units other than the structural unit represented by formula (1) and the structural unit represented by formula (2). When the polymer contains a structural unit represented by formula (11) or a structural unit represented by formula (12), the polymer may further contain other structural units other than the structural unit represented by formula (11) and the structural unit represented by formula (12).

When the organic compound having a functional group containing a sulfur atom is a polymer, the molecular weight (weight average molecular weight) of the polymer may be 200 or more, or 250 or more. The molecular weight (weight average molecular weight) of the polymer may be 100,000 or less, 70,000 or less, 10,000 or less, or 7,000 or less. The molecular weight of the polymer may be 200 or more and 100,000 or less, 70,000 or less, 10,000 or less, or 7,000 or less, or 250 or more and 100,000 or less, 70,000 or less, 10,000 or less, or 7,000 or less. The weight average molecular weight is a polystyrene-equivalent value using a calibration curve with standard polystyrene in gel permeation chromatography (GPC).

At least a portion of the organic compound (or polymer) attached to the surface of the carrier particle may be covalently bonded to the organic polymer serving as the carrier particle. For example, if the organic polymer has a reactive group (e.g., an epoxy group), the organic compound can be covalently bonded to the organic polymer by reaction of the reactive group with, for example, an amino group.

The ratio of the amount of organic compound to the mass of the carrier particles may be, for example, 5 to 50% by mass, or 10 to 40% by mass. The amount of amino groups in the adsorbent particles may be 0.1 to 100 mmol, 0.5 to 100 mmol, 0.1 to 20 mmol, or 0.5 to 20 mmol per 1 g of adsorbent particles.

The amount of amino groups in the adsorbent particles or in the base particles described below can be determined by measuring the amount of sulfuric acid consumed by reaction with the amino groups by titration with sodium hydroxide. The method for measuring the amount of amino groups in the base particles includes the following operations.
1) Methanol is added to the base particles (A) (g), and the resulting dispersion is heated at 75° C. for 30 minutes.
2) The base particles are collected from the dispersion by suction filtration on a filter. While continuing suction, pure water is added to the base particles on the filter to replace the methanol with pure water, and then the base particles are conditioned using a small amount of 0.1 M aqueous sodium hydroxide solution. The base particles are then washed with pure water until the filtrate becomes neutral.
3) The washed base particles are transferred to a glass container using a small amount of pure water, and the total amount of pure water in the container is adjusted to (B) g.
4) (C) g of 0.05 M sulfuric acid is added to the dispersion in the container, and then the dispersion in the container is stirred at room temperature for 30 minutes at 150 rpm.
5) (D) g of the supernatant of the dispersion is taken, and purified water is added thereto to adjust the liquid volume.
6) The diluted supernatant is titrated with 0.01 M aqueous sodium hydroxide solution, and the amount (E) mL of aqueous sodium hydroxide solution required for neutralization is recorded.
7) The amount of amino groups is calculated according to the following formula.
Amount of amino groups (mmol/g)=[{0.1×C×D/(B+C)−0.01×E}×(B+C)/D]/A

The diglycolic acid residue may be a monovalent group bonded to an amino group in an organic compound having an amino group and a functional group containing a sulfur atom, for example, as represented by the following formula (21) or (22). The amino group in the formula is the amino group of the organic compound, and the portion excluding the amino group is the diglycolic acid residue. The diglycolic acid residue interacts with the rare earth complex, allowing the adsorbent particles to adsorb the rare earth element.

The adsorbent particles can be produced, for example, by a method that includes preparing a base particle that does not have diglycolic acid residues and that includes a carrier particle and the above-mentioned organic compound attached to the surface of the carrier particle, and binding diglycolic acid or its anhydride to the organic compound, thereby forming the adsorbent particles. More specifically, diglycolic acid or its anhydride can be bound to the amino group of the organic compound.

The base particles are produced by attaching the organic compound to the surface of the carrier particles. One example of a method for preparing base particles when the carrier particles contain an organic polymer having a reactive group includes generating carrier particles, which are porous particles, by suspension polymerization in a reaction liquid containing a monomer component including a monomer having a reactive group, a porosifying agent, and an aqueous medium, and bonding the organic compound to the organic polymer by reaction between the reactive group and the organic compound.

The porogen used to form the porous particles is a component that promotes phase separation of the particles during polymerization, thereby forming the porous polymer particles. One example of a porogen is an organic solvent. Examples of organic solvents that can be used as porogens include aliphatic or aromatic hydrocarbons, esters, ketones, ethers, and alcohols. The porogen can include, for example, at least one selected from the group consisting of toluene, xylene, cyclohexane, octane, butyl acetate, dibutyl phthalate, methyl ethyl ketone, dibutyl ether, 1-hexanol, 2-octanol, decanol, lauryl alcohol, and cyclohexanol.

The amount of the porosifying agent may be 0 to 300% by mass based on the total amount of the monomer components. The porosity of the porous polymer particles can be controlled by the amount of the porosifying agent. The size and shape of the pores in the porous polymer particles can be controlled by the type of porosifying agent.

The aqueous medium may contain water. This water may function as a porosifying agent. For example, when an oil-soluble surfactant is added to the reaction solution, particles containing the monomer and the oil-soluble surfactant are formed, and the particles can absorb water to promote phase separation within the particles. By removing one of the phases from the phase-separated particles, the particles are made porous.

The aqueous medium includes water or a mixed solvent of water and a water-soluble solvent (e.g., a lower alcohol). The aqueous medium may include a surfactant. The surfactant may be an anionic, cationic, nonionic, or zwitterionic surfactant.

The reaction liquid for suspension polymerization may contain a polymerization initiator. Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide, lauroyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, tert-butylperoxy-2-ethylhexanoate, and di-tert-butyl peroxide; and azo compounds such as 2,2'-azobisisobutyronitrile, 1,1'-azobiscyclohexanecarbonitrile, and 2,2'-azobis(2,4-dimethylvaleronitrile). The amount of the polymerization initiator may be 0.1 to 7.0 parts by mass relative to 100 parts by mass of the monomer component.

The reaction liquid may contain a dispersion stabilizer to improve the dispersion stability of particles containing monomer components. Examples of dispersion stabilizers include polyvinyl alcohol, polycarboxylic acid, celluloses (hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, etc.), and polyvinylpyrrolidone. These may be used in combination with inorganic water-soluble polymer compounds such as sodium tripolyphosphate. The dispersion stabilizer may be polyvinyl alcohol or polyvinylpyrrolidone. The amount of dispersion stabilizer may be 1 to 10 parts by mass per 100 parts by mass of monomer.

The reaction liquid for suspension polymerization may contain water-soluble polymerization inhibitors such as nitrites, sulfites, hydroquinones, ascorbic acids, water-soluble B vitamins, citric acid, and polyphenols.

The polymerization temperature for suspension polymerization can be appropriately selected depending on the types of monomer and polymerization initiator. The polymerization temperature may be 25 to 110°C, or 50 to 100°C.

The resulting porous particles (carrier particles) may be washed and dried as necessary, and then the reactive groups of the organic compound, such as amino groups, may be reacted with the reactive groups of the organic polymer. This reaction may be carried out, for example, in a reaction liquid containing the carrier particles, the organic compound, and a solvent, with heating as necessary. The solvent is not particularly limited, and may be, for example, water.

After washing and drying the base particles as necessary, diglycolic acid or its anhydride is bonded to a reactive group such as an amino group in the organic compound attached to the carrier particles. This reaction can be carried out, for example, in a reaction liquid containing the base particles, diglycolic acid or its anhydride, and a solvent, with heating as necessary. The solvent is not particularly limited, but may be, for example, tetrahydrofuran. This reaction forms adsorbent particles into which diglycolic acid residues have been introduced. The formed adsorbent particles are washed and dried as necessary.

Substrate particles containing carrier particles and an organic compound attached to the surface of the carrier particles may be used to obtain adsorbent particles or separation particles to which ligands other than diglycolic acid residues have been introduced. The average particle size of the substrate particles is usually substantially the same as the average particle size of the adsorbent particles.

Rare earth elements can be efficiently recovered by a method that includes contacting the adsorbent particles with a solution containing rare earth elements, thereby adsorbing the rare earth elements onto the adsorbent particles, and then contacting the adsorbent particles with an acidic solution containing an acid, thereby desorbing the rare earth elements from the adsorbent particles.

The temperatures of the solution for adsorption and the acidic solution for desorption are not particularly limited, but may be, for example, 15 to 35°C. The contact time between the solution for adsorption and the adsorbent particles may be, for example, 20 seconds or more, or 40 seconds or more, and may be 48 hours or less. The contact time between the acidic solution for desorption and the adsorbent particles may be, for example, 5 seconds or more, or 10 seconds or more, and may be 6 hours or less.

The recovery method using the adsorbent particles according to this embodiment enables efficient recovery of rare earth elements based on the large amount of adsorption by the adsorbent particles. In addition, the adsorbent particles according to this embodiment are more resistant to acid than adsorbents that contain silica particles as carrier particles, and therefore have the advantage of being less prone to deterioration when used repeatedly.

The pH of the solution when adsorbing the rare earth elements to the adsorbent particles may be about 1.0 to 2.0. The acid concentration of the acidic solution for desorbing the rare earth elements is adjusted to a strength strong enough to adequately desorb the rare earth elements. For example, the acid concentration of the acidic solution may be 2N or less, 1N or less, or 0.5N or less. The adsorbent particles according to this embodiment can desorb rare earth elements with high efficiency even when a relatively weak acidic solution is used. Using a weak acidic solution is beneficial not only in terms of suppressing deterioration of the adsorbent but also in terms of reducing the environmental load. The acidic solution may be, for example, hydrochloric acid.

The rare earth element to be recovered may be any of scandium, yttrium, and lanthanides, or may be a lanthanide such as dysprosium or neodymium. The solution containing the rare earth element to be recovered may be an aqueous solution. The rare earth element in the solution is usually dissolved in a solvent (e.g., water) as a cation.

The adsorbent particles may be used as a column packing material. FIG. 1 is a schematic diagram showing one embodiment of a packed column. The packed column 10 shown in FIG. 1 includes a column body 11 (column tube), a connection part 12, and a column packing material 13 containing the adsorbent particles according to the embodiment described above. The connection parts 12 are arranged at both ends of the column body 11 to connect the column body 11 to a column chromatography device. The column packing material 13 is packed in the cylindrical column body 11. The material of the column body 11 and the connection part 12 is not particularly limited, and may be stainless steel or a resin such as polyether ether ketone (PEEK).

The column packing material 13 containing the adsorbent particles is usually packed into the column body 11 together with a solvent. The solvent is not particularly limited as long as it is a solvent in which the adsorbent particles can be dispersed, but it may be water, for example.

When recovering rare earth elements using a packed column, for example, a solution containing the rare earth elements is passed through the packed column, and then an acidic solution is passed through the packed column.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples.

1. Preparation of adsorbent particles <Example 1>
[Base particle]
Porous polymer particles made of a divinylbenzene-glycidyl methacrylate copolymer, a styrene-based polymer, were prepared as carrier particles. 1.0 g of these porous polymer particles were added to methanol, and the suspension was agitated to wet the porous polymer particles with methanol. The suspension was then filtered while maintaining a wet state using pure water, thereby replacing the methanol with pure water. Next, the pure water in the suspension was replaced by 12 g of an aqueous solution (concentration 20% by mass) of diallylamine hydrochloride sulfur dioxide copolymer (weight average molecular weight 5000, "PAS-92", manufactured by Nittobo Medical Co., Ltd.), which is a compound (polymer) having a sulfonyl group and an amino group, in the same manner, and 1.3 g of a 50% by mass aqueous solution of sodium hydroxide was further added. The obtained suspension was heated at 50°C for 3 hours to promote the reaction between the epoxy group of the porous polymer particles and the diallylamine sulfur dioxide copolymer. The porous polymer particles taken out by filtration were thoroughly washed with water and then dried at 50°C for 15 hours to obtain base particles into which the diallylamine sulfur dioxide copolymer was introduced. The average particle size of the obtained base particles was 220 μm, and the amount of amino groups per 1 g of the base particles was 1.8 mmol.

[Adsorbent particles]
1.0 g of the base particles and 4.7 g of diglycolic anhydride were reacted in tetrahydrofuran for 8 hours at 50° C. The particles were filtered out, thoroughly washed with water, and then dried at 50° C. for 15 hours to obtain adsorbent particles having diglycolic acid residues introduced therein.

Example 2
Base particles were obtained in the same manner as in Example 1, except that 12 g of the aqueous solution of diallylamine hydrochloride sulfur dioxide copolymer (concentration 20% by mass) was replaced with a mixture of 12 g of the aqueous solution of diallylamine hydrochloride sulfur dioxide copolymer (concentration 20% by mass) and 12 g of pure water. The average particle size of the obtained base particles was 220 μm, and the amount of amino groups per 1 g of base particles was 1.8 mmol. Adsorbent particles having diglycolic acid residues introduced therein were obtained by the same operation as in Example 1, except that the obtained base particles were used.

Example 3
Base particles were obtained in the same manner as in Example 1, except that 12 g of an aqueous solution of diallylamine hydrochloride sulfur dioxide copolymer (concentration 20% by mass) was changed to 12 g of an aqueous solution of diallylamine hydrochloride sulfur dioxide copolymer (concentration 30% by mass). The average particle size of the obtained base particles was 220 μm, and the amount of amino groups per 1 g of base particles was 2.1 mmol. Adsorbent particles having diglycolic acid residues introduced therein were obtained by the same operation as in Example 1, except that the obtained base particles were used.

<Comparative Example 1>
Porous polymer particles made of the same divinylbenzene-glycidyl methacrylate copolymer as in Example 1 were prepared as carrier particles. The porous polymer particles were added to methanol, and the suspension was stirred by rocking to wet the porous polymer particles with methanol. Thereafter, the suspension was filtered while maintaining a wet state using pure water, thereby replacing the methanol with pure water. Subsequently, the pure water in the suspension was replaced with ethylenediamine in the same manner. The suspension was heated at 50°C for 3 hours to promote the reaction between the epoxy groups of the porous polymer particles and ethylenediamine. The porous polymer particles taken out by filtration were thoroughly washed with ethanol and water, and then dried at 80°C for 15 hours to obtain base particles into which ethylenediamine had been introduced. The average particle size of the obtained base particles was 220 μm, and the amount of amino groups per 1 g of base particles was 2.0 mmol. Except for using the obtained base particles, the same operation as in Example 1 was performed to obtain adsorbent particles into which diglycolic acid residues had been introduced.

Quantitative analysis
The adsorbent particles obtained in Examples 1 to 3 or Comparative Example 1 were analyzed by combustion ion chromatography to quantify the content of sulfur atoms (S content) based on the mass of the adsorbent particles. In addition, the adsorbent particles were subjected to elemental analysis by a combustion method to quantify the content of nitrogen (N content) based on the mass of the adsorbent particles. The results are shown in Table 1.

<Liquid flow test>
The adsorbent particles obtained in the examples and comparative examples into which diglycolic acid residues were introduced were packed in a pressure-resistant column tube with an inner diameter of 5.0 mm so that the carrier height was 50 mm (gel volume = 0.98 ml). Next, an aqueous sulfuric acid solution adjusted to pH = 1.5 was passed through at a flow rate of 1.64 mL / min for 5 minutes. Then, a sulfuric acid solution (also called the original solution) containing 5 ppm of dysprosium (Dy) and 1000 ppm of Fe and having a pH = 1.5 was passed through at a flow rate of 1.64 mL / min for 1 hour, and the liquid after passing through was collected and used as the passing liquid. The Dy concentration and Fe concentration of the passing liquid were measured using an ICP emission spectrometer, and the Dy adsorption rate and Fe adsorption rate were calculated using the following formula.
Dy adsorption rate (%)=(Dy concentration of original solution (5 ppm)−Dy concentration of passed solution)×100
Fe adsorption rate (%)=(Fe concentration in original solution (1000 ppm)−Fe concentration in passed solution)×100

As shown in Table 1, when the adsorbent particles of Examples 1 to 3 were used, the Dy adsorption rate was 38% or more and the Fe adsorption rate was 11.3% or less, whereas when the adsorbent particles of Comparative Example 1 were used, the Dy adsorption rate was 11% and the Fe adsorption rate was 20%. Thus, it was confirmed that the adsorbent particles of the Examples adsorb a sufficiently large amount of rare earth elements. Furthermore, the adsorption rate of rare earth elements by the adsorbent particles of the Examples is clearly greater than that by the adsorbent particles of the Comparative Example, and it can be seen that the adsorption of Fe can be suppressed.

10...packed column, 11...column body, 12...connection, 13...column packing material.

Claims (8)

A carrier particle containing an organic polymer including a monomer unit derived from a styrene-based monomer;
an organic compound having a sulfonyl group and an amino group attached to the surface of the carrier particle;
and a diglycolic acid residue bonded to said amino group,
The adsorbent particles have a sulfur atom content of at least 0.5 mass % based on the mass of the adsorbent particles. The adsorbent particles according to claim 1, wherein the content of sulfur atoms in the adsorbent particles is 20% by mass or less based on the mass of the adsorbent particles. The organic compound is a polymer having a main chain including a constitutional unit represented by the following formula (1) or a constitutional unit represented by the following formula (3) and a constitutional unit represented by the following formula (2),

In formula (1), R ¹ represents an alkylene group having 1 to 4 carbon atoms or a single bond, R ² represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom,
3. The adsorbent particle according to claim 1 or 2, wherein in formula (3), m and n each independently represent an integer of 1 or more and 3 or less . The adsorbent particles according to any one of claims 1 to 3, wherein the content of nitrogen atoms in the adsorbent particles is 0.2 mass% or more based on the mass of the adsorbent particles. The adsorbent particles according to any one of claims 1 to 4, wherein the carrier particles are porous polymer particles. The adsorbent particles according to any one of claims 1 to 5 are used to recover rare earth elements. A packed column comprising a column body and the adsorbent particles according to any one of claims 1 to 6 packed in the column body. contacting the adsorbent particles according to any one of claims 1 to 5 with a solution containing a rare earth element, thereby adsorbing the rare earth element onto the adsorbent particles;
and desorbing the rare earth elements from the adsorbent particles by contact with an acidic solution comprising an acid.

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