JPS628145B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses a complexing agent and an ion exchange column to
This invention relates to a method for separating mixed elements into each element in a high concentration and high purity state. Conventionally, one of the most effective methods for separating and obtaining mixed elements in their pure form is the method of using an ion exchange tower to adsorb and develop mixed elements using acceptors and complexing agents to separate them chromatically. There is. Although this method can separate elements of extremely high purity, its biggest drawback is that the concentration of the elements in the eluted solution is extremely dilute. Therefore, not only is a large volume of complexing agent solution required, but also the recovery of elements from the eluate after separation is inefficient due to precipitation, filtration, etc. due to the dilute solution, making it difficult for industrial use. It wasn't practical. In order to increase the concentration of the eluted elements, it is possible to increase the concentration of the complex forming agent, but this is limited by the solubility of the complex forming agent, and if the concentration is higher than that, the complex forming agent will precipitate in the ion exchange column. However, the inside of the tower becomes clogged, making separation difficult. The present inventors have conducted intensive research into a method for separating mixed elements using a complexing agent and an ion exchange tower, with the aim of maintaining the high purity separation state that is characteristic of this method and separating it in a highly concentrated state. As a result, they discovered that when the tip of the adsorption band of an element reaches the column outlet, the complex-forming agent does not precipitate inside the column even when eluted with a high concentration of complex-forming agent, leading to the present invention. . That is, the present invention provides a method for chromatographic separation of elements using a complexing agent and an ion exchange column, in which the adsorption band of the element is moved, and when its tip reaches the end of the ion exchanger packed in the column, This is an element separation method characterized by elution by increasing the concentration of a complexing agent, and is particularly excellent for separating rare earth elements in a high purity and high concentration state using a cation exchange column. . Since the present invention makes it possible to perform separation in a high concentration state, it is not only possible to significantly reduce the volume of the eluate compared to conventional methods, but also to improve the process of recovering elements from the eluate. It has advantages such as improved precipitation efficiency and improved filtration and water washing efficiency. The configuration of the present invention will be explained in more detail below. A typical example of the chromatographic development operation used in the present invention consists of the following steps. () A receptor solution is supplied to a column filled with an ion exchanger, and the ion exchanger in the column is converted into a receptor type. () Mixed element solutions (even if they contain complexing agents)
) is supplied to form a mixed element adsorption zone. () Supply a solution containing a complexing agent at a concentration commonly used and move the adsorption zone until the tip of the adsorption zone reaches the column outlet. () Switch to a solution containing a high concentration of complexing agent,
Continuing the elution, the solution flowing out from the column outlet is divided into fractions and collected. In the present invention, the ion exchanger is first regenerated by the operation in (), then a mixed element adsorption zone is formed by the operation in (), and the adsorption zone is moved by the operation in (). What is important here is that in the above operations () and (), when the tip of the mixed element adsorption zone reaches the column outlet, elution is performed with a solution containing a high concentration of complex forming agent. If the same operation is performed with the tip of the band not reaching the column outlet, the complex forming agent will precipitate within the column, making separation impossible. The concentration of the conventional eluent is
The concentration ranges from 0.1 to 30mM/, but in the present invention, the concentration of the eluent that is flowed from the time when the tip of the adsorption zone reaches the column outlet is preferably 15 to 50 times the above 0.1 to 30mM/. The lower limit is determined by the magnitude of the effect of the present invention, and the upper limit is determined by ensuring a predetermined width of the adsorption zone. The mixed element in the present invention may be any element as long as it can be made into an ionic state. Cations can be separated using a cation exchanger, and anions can be separated using an anion body. The present invention will be explained below using as an example a method for separating rare earth elements, which are said to be the most difficult to separate. Rare earth elements are elements of the lanthanide group, namely lanthanum, cerium, praseodymium, neodymium, promethium, samarium, eurobium,
It is a general term for 17 elements, consisting of the 15 elements gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, plus scandium and yttrium. The salts of the rare earth element mixed solution containing the complex forming agent used in the present invention are single or mixed salts such as Cl ^- , SO ^2- ₄ , NO ^- ₃ , ClO ^- _{3 ,} etc., and when used as a rare earth salt, soluble You can use any salt you like. Commonly used complexing agents include citric acid, tartaric acid, oxalate, acetate, hydrochloric acid, sulfuric acid, polycarboxylic acid, rhodan salt, cyanide, ammonia, etc. For example, in the case of rare earth elements teeth,
Examples of effective coordination compounds include ethylenediaminetetraacetic acid (EDTA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), N-hydroxyethylethylenediaminetriacetic acid, ethylene glycol-bis(2-aminoethyl)ether-N ，
N,N',N'-tetraacetic acid, diethylenetriaminepentaacetic acid, bis(2-aminoethyl)ether-
Aminopolyacetic acids such as NN, N′, N′-tetraacetic acid, nitrilotriacetic acid, iminodiacetic acid, citric acid, lactic acid,
Examples include oxycarboxylic acids such as glycolic acid, malic acid, and tartaric acid. The mixed solution of the complex-forming agent and the rare earth element is preferably adjusted to a pH at which the rare-earth element ions in the raw materials do not hydrolyze and form a precipitate, and at which the rare-earth element and the complex-forming agent can form a complex. This preferred pH is determined by the dissociation constant of the complex forming agent, but is generally PH 0.1-10, more preferably PH 1-6. For example, when ethylenediaminetetraacetic acid (EDTA) is used as a complexing agent,
It is preferable to adjust the pH to 2 to 4. It is desirable to adjust the acceptor solution to a pH that does not cause precipitation due to hydrolysis of the container and has adsorption power to the cation exchanger.
When ( ) ion is used as an acceptor, the pH is preferably 0.1 to 6.9, more preferably PH 1 to 4.
In addition, when H ⁺ is used as an acceptor, the preferred H ⁺
The concentration is 0.01M/or more, the more preferable H ⁺ concentration is
It is 0.1M/~5M/. When the acceptor used in the present invention is an anion exchanger, I ^- , C ₆ H ₅ O ^- , HSO ^- ₄ , NO ^- ₃ , Br ^- ,
CN ^- , HSO ^- ₃ , NO ^- ₂ , Cl ^- , HCO ^- ₃ , H ₂ PO ^- ₄ ,
HCOO ^- , CH ₃ COO ^- , OH ^- , F ^-, etc., and in the case of cation exchangers, Li ^- , H ⁺ , Na ⁺ , NH ⁺ ₄ ,
K ⁺ , Pb ⁺ , Ag ⁺ , UO ²⁺ ₂ , Mg ²⁺ , Zn ²⁺ , CO ²⁺ ,
Cu ²⁺ , Cd ²⁺ , Mn ²⁺ , Be ²⁺ , Ca ²⁺ , Sr ²⁺ , Pb ²⁺ ,
Ba ²⁺ , Cr ²⁺ , etc. Preferred acceptors for rare earth elements include those that have a greater complex-forming ability than rare earth elements, such as:
Pb ²⁺ , Pb ²⁺ , Ni ²⁺ , Cu ²⁺ , Hf ⁴⁺ , Zr ⁴⁺ , Ga ³⁺ ,
Ti ³⁺ , In ³⁺ , Fe ³⁺ , V ³⁺ and H ⁺ (hydrogen ions)
etc. The pH of the complex forming agent solution used for adsorption zone movement and elution is such that when the complex forming agent comes into contact with the rare earth element, the rare earth element ions will not be hydrolyzed and precipitate. It is necessary to adjust the pH to such a level that complex formation progresses between the cation exchangers and the adsorption power to the cation exchanger decreases, and generally the pH is adjusted to such a level that the dissociation of the complex forming agent progresses. It is preferable. For example, when EDTA is used as a complexing agent, the pH is 4 to 11, more preferably 5 to 8. For regeneration of cation exchangers or for solution
Acids or alkalis are used to adjust the pH; examples of these acids and alkalis include hydrochloric acid,
Inorganic acids such as sulfuric acid, nitric acid, perchloric acid, hydrobromic acid, etc., or mixtures of these acids, and sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, sodium carbonate, potassium carbonate , lithium carbonate, alkalis such as aqueous ammonia, or mixtures thereof. From the viewpoint of product treatment, the acid is preferably sulfuric acid or hydrochloric acid, and the alkali is preferably aqueous ammonia. The preferred temperature for carrying out the present invention is -10°C to
The temperature suitable for each case can be selected between 150℃. More preferably, the temperature is 10°C to 120°C. For example using H ⁺ as acceptor and as complexing agent
When using EDTA, DCTA, preferably 70
The temperature is ~150 °C, more preferably 85-120 °C, and 10-60 °C when using Fe() ion as acceptor and EDTA as complexing agent.
A range of is preferred. The anion exchanger used in the present invention has 〓NX, 〓P, 〓S, etc. as an ion exchange group. For example, Lewis (Lewis) copolymer beads of styrene and divinylbenzene such as AlCl ₃
It can be obtained by chloromethylation with chloromethyl ether using an acid catalyst and further reaction with a tertiary amine. In addition, copolymer beads of ethyl acrylate and divinylbenzene were
An amino group can also be introduced through an amide bond by reacting with a polyamine such as dimethylaminopropylamine. Furthermore, a condensation product of m-phenylenediamine and formalin, a reaction product of polyethyleneimine and epichlorohydrin, etc. can also be used. On the other hand, the preferred cation exchanger used in the present invention is a monomer or a copolymer made of a monomer having a vinyl group, and the crosslinking monomer weight% in the monomer is 4% or more. It is an ion exchanger synthesized from a certain copolymer. A preferred configuration of this type of resin is a sulfonated polymer crosslinked product synthesized by addition copolymerization with styrene, vinyltoluene, divinylbenzene, etc. as the main monomer components; halomethylstyrene, methylvinylketone, A sulfonated addition polymer consisting mainly of a monomer having an active group such as epoxybutadiene or acrylamide and a crosslinking monomer such as divinylbenzene or triallylisocyanurate; sodium vinylsulfonate, methacrylic acid, Examples include those copolymerized with a crosslinking monomer and a monomer having a functional group that can serve as an exchange group, such as acrylic acid and esters thereof such as alkyl esters and phenyl esters. The monomers used in the production of the cation exchange resin matrix used in the present invention include styrene, methylstyrene, ethylstyrene, vinylnaphthalene, 3,
4,6-trimethylstyrene, chlorstyrene,
Methoxystyrene, N,N-dimethylaminostyrene, nitrostyrene, chloromethylstyrene,
Styrene derivatives such as trifluorostyrene, trifluoromethylstyrene, aminostyrene; butadiene, acrylonitrile derivatives; acrylic acid,
Acrylic acid esters such as methacrylic acid, methyl acrylate, chloromethyl acrylate, methacrylic acid esters such as cyclohexyl methacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, methyl methacrylate, diethyl maleate, diethyl fumarate; methyl vinyl Vinyl ketones such as ketones and ethyl isopropyl ketone; vinylidene compounds; acrylamide derivatives;
Fatty acid vinyl esters such as vinyl acetate, vinyl butyrate, and vinyl cabrate; Epoxybutadiene; Vinyl sulfonic acid ethyl ester, vinyl sulfonic acid phenyl ester, styrene sulfonic acid, styrene sulfonate, styrene sulfonic acid butyl ester, methyl vinyl sulfonate sulfur-containing monomers such as In addition, the crosslinking monomers used in the production of the cation exchange resin base include divinylbenzene, divinyltoluene, divinylnaphthalene, divinylethylbenzene, trivinylbenzene, divinyldiphenylmethane, divinylbenzyl, divinylsulfone, divinylketone, bis (vinylpyridinoethyl)ethylenediamine, diallyl phthalate,
triallylamine, N,N'-ethylene diacrylamide, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate,
Examples include trimethylpropane triacrylate, triallyl isocyanurate, diallylmelamine, etc. A more preferred cation exchanger is a sulfonated polymer crosslinked product synthesized by addition copolymerization using styrene, vinyltoluene, ethylvinylbenzene, and divinylbenzene as main components;
Sulfonated addition copolymers whose main components are monomers with active groups such as chloromethylstyrene, methylethylketone, epoxybutadiene, acrylamide, and crosslinking monomers such as divinylbenzene and triallylisocyanurate; vinyl The main component is a sulfur-containing monomer that can serve as an exchange group for sulfonic acid phenyl ester, styrene sulfonate, styrene sulfonic acid butyl ester, methyl vinyl sulfide, etc., and is copolymerized with a crosslinking monomer as necessary. and their reactants, and cation exchange resins such as condensation polymers of phenolsulfonic acid and formaldehyde. Note that in the case of a resin starting from a styrene-divinylbenzene copolymer, it is particularly easy to set specific conditions. One of the preferred methods in the resin granule synthesis step is suspension polymerization. When performing addition polymerization or polycondensation of oil-soluble monomers, it is desirable to carry out O/W type suspension. In this case, by selecting appropriate conditions, a narrow particle size distribution can be achieved without a classification operation. You can get the following. In addition, in the case of addition polymerization or polycondensation of water-soluble monomers, W/O type suspension is required.
Although it is technically more difficult than the O/W type, as long as suspended water droplets can be made, particles with a relatively narrow particle size distribution can be obtained. Suspensions when using oil-soluble monomers include gum arabic, gamboge, rosin, pectin, alginate, gum tragacanth, agar, methylcellulose, starch, carboxymethylcellulose,
Karaya gum, mucilage such as gelatin, synthetic polymers such as sodium polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone, carphobol, diacetoolein, magnesium aluminum silicate, verma gel, hydrated magnesium silicate, titanium oxide, zinc oxide, calcium carbonate, Inorganic substances such as talc, barium sulfate, calcium phosphate, aluminum hydroxide, and silicic anhydride are preferred, and salts such as common salt, PH regulators, and emulsifiers are also preferably added as necessary. When water is suspended in oil, it is preferable to use a surfactant in addition to the polymer suspending agent, and sorbitan ester, sorbitan ester ether, fatty acid soap, fatty acid glyceride, etc. are particularly desirable. The second preferred cation exchanger used in the present invention
is an ion exchanger that has a substance with ion exchange ability on an organic carrier. As the organic carrier, a polymer carrier such as polyethylene, polypropylene, polystyrene, or styrene-divinylbenzene copolymer is used, and a substance with cation exchange ability is added to it through adsorption, reaction, graft polymerization, etc. Alternatively, a desired substance can be obtained by a method in which a cation exchange group is provided on the surface of an organic carrier through a reaction. For example, a cation exchanger obtained by sulfonating a styrene-divinylbenzene copolymer is desirable. Third preferred cation exchanger used in the present invention
is an ion exchanger that has a substance with ion exchange ability on an inorganic carrier. The inorganic carrier is preferably carbon, silica gel, zeolite, activated clay, glass beads, etc.
It is made with a substance that has cation exchange ability through reaction, graft polymerization, etc. Such inorganic carrier ion exchangers are often used in the specialized field of analytical chemistry. In addition, the ion exchanger using glass beads as a carrier disclosed in Japanese Patent Application Laid-Open No. 50-32085, the known carrier-based ion exchanger described in the publication, and the specification of Japanese Patent Application No. 102102-1982 The disclosed silica gel-based ion exchangers and the known carrier-based ion exchangers described therein are advantageously used. Among these cation exchangers, those having a sulfone group are preferred for the separation of rare earth elements, and are highly effective because of their excellent separation performance. More preferred cation exchangers have a volume porosity of 0.5 or more and 0.88 or less. If it is less than 0.5, the diffusion coefficient will decrease and separation efficiency will deteriorate, and if it is more than 0.88, the adsorption amount will suddenly decrease and separation will become poor. The volumetric porosity Rv in the present invention is expressed by the following equation. Rv=Pv/Sv Here, Sv represents the resin volume, Pv represents the pore volume within the resin, and Sv and Rv are measured by the following measurement method. (1) Measuring Rv: Immerse the cation exchange resin in the hydrogen ion form in water. of water-containing resin is dehydrated by centrifugal force so that the amount of water removed in the first stage is constant (for water-containing resin, as the centrifugal force (dehydrator rotation speed) increases, the cumulative value of the amount of water removed becomes constant, and further centrifugation When the force is increased, the amount of water removed increases again and becomes constant again, but the centrifugal force makes the amount of water removed in this first stage (initial) constant. Usually 500
~9000rpm). The water in the resin after dehydration is evaporated in a vacuum dryer. The amount of water evaporated at this time represents the amount of water in the pores, that is, the pore volume (Pv). (2) Measurement of Sv: The true volume of the dried cation exchange resin is measured in a device that is not affected by moisture, and the resin volume (Sv) is calculated by adding the pore volume (Pv) to this true volume. ). Next, the present invention will be explained in more detail with reference to Examples. Example 1, Comparative Example 1 As an ion exchange column, a cation exchange resin obtained by sulfonating a styrene-divinylbenzene copolymer (volume porosity 0.7, average (particle size 120μ) and the entire column was kept at 90°C. Next, 0.5NH ₂ SO ₄ was flowed from the top of the column at a rate of 140 ml per minute for about 15 minutes.
All the resin was regenerated into hydrogen ion form. next
Pr7.5mM/, Nd7.5mM/, EDTA15mM/
An aqueous solution containing 10% was flowed from the top of the column, forming an adsorption zone in 1/3 of the column. Next, develop with an aqueous solution containing EDTA 15mM/, NH ₄ OH 45mM/, and when the tip of the adsorption zone reaches the column outlet, EDTA 100mM/,
Elution was performed by switching to an aqueous solution containing 300 mM of NH ₄ OH. The eluate was fractionated and collected from a fraction collector connected to the bottom of the column. The concentration of rare earth elements in each fraction was measured using a fluorescent X-ray analyzer. Next, combine the fractions with purity >99%,
H ₂ SO ₄ was added to adjust the pH to 1.5. This results in
EDTA was precipitated, and after filtration, NH ₄ OH was added to adjust the pH to 9. As a result, the rare earth elements were precipitated as hydroxides, which were then filtered and dried at 110°C for 5 hours.
The results are shown in Table-1. On the other hand, as Comparative Example 1, the same operation as above was performed except that the concentration of EDTA was not changed during the elution. The results are shown in Table 1.
Example 1, which had a higher fraction average molar concentration, had a better recovery rate.

[Table] Examples 2 to 4, Comparative Examples 2 and 3 Using the same ion exchange tower as in Example 1, adsorption liquids of various concentrations were prepared. Each liquid was poured from the top of the column to form an adsorption zone in one-third of the entire column. Next, a solution containing 15mM EDTA and 45mM NH ₄ OH was flowed until the tip of the adsorption zone reached the column outlet, and then a solution containing EDTA with a different concentration was flowed.
Analysis and recovery were performed in the same manner as in Example 1. The results are shown in Table-2. Further, as Comparative Example 2, the same procedure as in Example 2 was carried out except that the concentration of EDTA was not changed even after the tip of the adsorption zone reached the tower outlet. Furthermore, as Comparative Example 3, the EDTA concentration in the adsorption solution was set to 60mM/, and adsorption started, but halfway through,
EDTA precipitated and could no longer be separated.

[Table] Comparative example 4 The tip of the adsorption zone was 10 cm before the tower outlet.
The same procedure as in Example 1 was carried out except that the EDTA concentration was changed to 100 mM. However, immediately after changing the EDTA concentration, EDTA precipitated in the column and could no longer be separated. As explained above, according to the present invention, in a method for separating mixed elements using a complex forming agent and an ion exchange column, it is possible to maintain a high purity separation state, which is a feature of this method, and to perform separation in a high concentration state. be.

Claims (1)

[Claims] 1. In a method for chromatographic separation of elements using a complex forming agent and an ion exchange column, when the adsorption band of the element is moved and its tip reaches the end of the ion exchanger packed in the column. , a method for chromatographic separation of elements, characterized in that elution is carried out by increasing the concentration of a complexing agent. 2. The separation method according to claim 1, wherein the rate of increase in concentration is 1.5 to 50 times. 3. The separation method according to claim 1, wherein the ion exchanger is a cation exchanger. 4 Claim 1 in which the element is a rare earth element
The separation method described in Items 1 to 3.