JPS6351721B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for selectively and efficiently collecting ionic substances such as metal ions dissolved in an aqueous solution or an organic solvent, which is characterized by using a fluoroalkyl group-containing compound as an ionophore. be. Conventionally, compounds with inclusion properties (hereinafter referred to as inclusion properties) such as chelate resins, ion exchange resins, and recently crown ethers and cryptands have been used to capture ionic substances such as metal ions by coordination or inclusion. compounds), and their polymerized products are also known. In general, clathrate compounds refer to compounds that have the ability to include not only ionic substances but also various other compounds to form clathrate compounds. It is called. Polymers such as chelate resins and ion exchange resins are
Although it has the advantage of being insoluble in water and making it easy to recover captured metals, it generally has low selectivity for metal ions and has the disadvantage of causing shape changes and deterioration. In addition, the meaning of polymerization is to place ligands involved in interaction with ionic substances in a certain space, and to express polymer effects such as locally increasing the concentration of the ligands. However, due to the irregularity of the primary structure in which ligands are irregularly arranged in the main chain, or the irregularity of the secondary structure due to changes in the conformation of the polymer main chain or side chains, metal ions, etc. can be selectively removed. However, it is insufficient in terms of effectively securing a precise space for capturing. Cyclic inclusion compounds such as crown ethers and cryptands have been developed with a focus on selectivity, but these generally require a large number of synthesis steps, which is an industrial disadvantage. . Also,
Products have been developed in which such inclusion compounds are introduced into the side chains of polymers to improve the efficiency of collecting metal ions, but this is similar to the case of the polymerized collection agents mentioned above. However, there are difficulties in achieving high selectivity. In addition to the above-mentioned methods of polymerization or cyclization, as a method for forming voids that selectively include ionic substances such as metal ions and locally increasing the concentration of functional groups involved in inclusion, A possible method is molecular aggregation. Based on this idea, the present inventor focused on the characteristic that fluoroalkyl groups, which are both hydrophobic and lipophobic, associate in water and most organic solvents, and developed compounds containing fluoroalkyl groups. The possibility of this as an ionophore has been investigated. As a result, as explained below, we found that a wide range of fluoroalkyl group-containing compounds are suitable ionophores for ionic substances such as metal ions. This enabled the separation and completed the present invention. Note that the meaning of inclusion as described herein does not include phenomena such as the formation of organic salts between an anion such as a carboxylate and a cation such as Ca2. An object of the present invention is to use a fluoroalkyl group-containing compound as a scavenger for ionic substances such as metal ions. Another object of the present invention is to provide a method for selectively and highly efficiently collecting ionic substances dissolved in an aqueous solution or an organic solvent using a fluoroalkyl group-containing compound. The fluoroalkyl group-containing compound according to the present invention has the general formula {R-(A) _a }- _o YX () [In the formula, R is a fluoroalkyl group having 3 to 20 carbon atoms, and A is a divalent or higher fluoroalkyl group. The polyvalent linking group a is 0 or 1, n is an integer of 1 or more, Y is a residue that can include an ionic substance, X is a residue that does not inhibit interaction with an ionic substance, and the X group is Y It may be bonded to the {R-(A) _a } _-o group via the group, or the Y group may be bonded to the {R(A) _a } _-o group via the X group. . ] It is a compound represented by The compound of the general formula has a fluoroalkyl group R
Due to the presence of
As a result, the functional groups in the residue Y that can include metal ions come close to each other, forming an inclusion field similar to that of a cyclic ionophore. In order for the association to be dense and stable, the R group is preferably a perfluoroalkyl group having 3 or more carbon atoms, but the structure may be linear, branched, or cyclic (for example, a group such as a cyclohexyl group). Alternatively, it may be a combination of these, or it may be one in which an oxygen atom intervenes in the main chain, such as (CF ₃ ) ₂ CFOCF ₂ CF ₂ -. In the general formula, examples of the polyvalent linking group A having a valence of two or more are -O-, -S-, -CO-, -SO ₂ -, -
N<, -CON<, -SO ₂ N<, etc., -(CH ₂ ) _p ,

[Formula] (where p is an integer from 1 to 5 represent ),

【formula】

[Formula] Aliphatic groups such as -CH ₂ CH ₂ N<, -CH ₂ CH ₂ S -, -CH ₂ CH ₂ SO ₂ N<, -CH ₂ CH ₂ CON<, or aliphatic groups containing heteroatoms. and

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

It may also contain an aromatic group such as [Formula]. Examples of functional groups constituting the residue Y that can include an ionic substance include a sulfonyl group, a sulfonamide, a carbonyl group, a carbonyl ester group, a urethane bonding group, a urea bonding group, and an ether bonding group. Some of the polyvalent linking groups A having a valence of two or more may also be involved in the inclusion of the ionic substance, and may be included in Y. In that sense, a is 0 or 1. The X residue is not directly involved in inclusion, but it affects the solubility of the compound represented by the general formula in organic solvents,
It affects the structure of the inclusion field, such as alkyl groups and aromatic groups. Table 1 shows specific examples of the fluoroalkyl group-containing compounds according to the present invention.

【table】

【table】

【table】

【table】

[Table] Although there are many specific methods for separating ionic substances using fluoroalkyl group-containing compounds as ionophores according to the present invention, they can be broadly classified into the following three aspects. The first embodiment is a method in which a fluoroalkyl group-containing compound is added to an aqueous solution or an organic solvent solution in which an ionic substance such as a metal ion is dissolved, and the ionic substance is included and separated at the liquid-solid interface. For example, this is carried out when the solubility of the fluoroalkyl group-containing compound in water and organic solvents is extremely low, such as 1 x 10 ^-4 % by weight or less. In the second embodiment, a fluoroalkyl group-containing compound is dissolved in an organic solvent that is almost immiscible with water,
This is a method for separating the ionic substances by bringing such an organic solvent solution into contact with an aqueous solution in which ionic substances are dissolved. In this case, the fluoroalkyl group-containing compound has a solubility in water of 2×10 ^-2
1% by weight or less, solubility in organic solvents
It is desirable that the content is ×10 ^-4 % by weight or more. This embodiment includes a liquid-liquid extraction method, a liquid membrane method, and the like. The third embodiment is a method of dissolving the fluoroalkyl group-containing compound according to the present invention in an organic solvent solution in which an ionic substance is dissolved, and then recovering the precipitated clathrate compound. When the fluoroalkyl group-containing compound according to the present invention is dissolved in an organic solvent, its association state changes depending on the type of organic solvent, and the selectivity for ionic substances also changes slightly accordingly. Therefore, the selectivity can be controlled to some extent by the nature of the solvent used, and the range of applications of fluoroalkyl group-containing compounds as ionophores is wide. In order to fully exhibit the properties of the fluoroalkyl group-containing compound according to the present invention as an ionophore, a solvent with a solubility parameter δ value of 7.5 or more is generally preferred, and a solvent with a solubility parameter δ value of 7.5 or more is most preferred. Specific examples include chloroform, dichloromethane, dichloroethane, tetrahydrofuran, ethyl acetate, and nitromethane. Ionic substances targeted by the collection method of the present invention include inorganic metal salts, organic metal salts, amino acids, etc., and metal salts are particularly suitable targets for collection. The clathrated ionic substances can be easily recovered by contacting them with mineral acids such as hydrochloric acid, sulfuric acid, and nitric acid, or aqueous solutions (eluents) such as ammonium carbonate, sodium bicarbonate, soda carbonate, and caustic soda. It is possible to repeatedly reuse compounds containing fluoroalkyl groups. For example, in liquid-liquid extraction, the organic layer from which ionic substances have been extracted can be brought into contact with an eluent and back extracted.
The organic layer is reusable. In this sense, the fluoroalkyl group-containing compound according to the present invention is suitable as a carrier for a liquid film method in which extraction and recovery steps are integrated. Next, an example of the substance separation method of the present invention will be shown,
The present invention will be explained in more detail. Example 1 A chloroform solution (7.0×10 ^-4 M, 20 ml) of each fluoroalkyl group-containing compound and each metal salt (uranyl acetate, NaCl, BaCl ₂ , CoCl ₂ , NiCl ₂ ,
CuCl ₂ , ZnCl ₂ , HgCl ₂ ) aqueous solution (7.0×10 ^-4 M,
Liquid-liquid extraction of the metal salts was performed by stirring with a magnetic stirrer at 37°C for 24 hours. The extraction amount was determined by quantifying the metal ions remaining in the aqueous solution (uranyl ion: arsenazo method, other metal ions: atomic absorption method). Table 2 shows the results.

[Table] Shown.
As described above, according to the substance separation method of the present invention, useful metals such as uranyl ions can be recovered. Example 2 Artificial seawater solution of uranyl acetate (7.0×0 ^-4 M, 20
Example ¹
It was carried out under similar conditions. Table 3 shows the extraction results.

【table】

[Table] As can be seen from this result, according to the method of the present invention, uranyl ions can be collected without being affected by coexisting metal ions. Next, remove the extracted chloroform layer by 20%
Back extraction was performed by contacting with 10 ml of ammonium carbonate aqueous solution for 20 minutes with stirring. As a result, 99.7% of uranyl ions were separated.

Claims (1)

[Claims] 1. To selectively and highly efficiently collect an ionic substance present in a liquid medium from the medium using a compound containing a fluoroalkyl group and capable of clathrating the ionic substance. A substance separation method characterized by: