WO2020049884A1

WO2020049884A1 - Lithium ion permselective membrane, lithium ion recovery device and lithium-containing compound recovery device using same, and lithium ion recovery method

Info

Publication number: WO2020049884A1
Application number: PCT/JP2019/028953
Authority: WO
Inventors: 裕介飯塚
Original assignee: 富士フイルム株式会社
Priority date: 2018-09-07
Filing date: 2019-07-24
Publication date: 2020-03-12
Also published as: JP2022001341A

Abstract

Provided are a lithium ion permselective membrane having excellent membrane formability and Li⁺ selectivity, a lithium ion recovery device and a lithium-containing compound recovery device having excellent Li⁺ selectivity, and a lithium ion recovery method. The lithium ion permselective membrane contains a lithium ion conductor and a specific polymer (B) having an anionic group.

Description

Lithium ion selective permeable membrane, lithium ion recovery apparatus and lithium-containing compound recovery apparatus using this membrane, and lithium ion recovery method

The present invention relates to a lithium ion selective permeable membrane. The present invention also relates to a lithium ion recovery device, a lithium-containing compound recovery device, and a lithium ion recovery method using the membrane.

Electric vehicles, which have less environmental impact than gasoline and diesel vehicles, have been widely used. Large lithium (Li) ion batteries mounted on electric vehicles include lithium-containing compounds such as Li ₂ CO ₃ (hereinafter, lithium-containing compounds, lithium atoms and / or lithium ions are collectively referred to as “lithium or the like”. Is used.) Lithium atoms are used when artificially producing tritium (tritium) as fuel for a nuclear fusion reactor. Therefore, the demand for lithium atoms and lithium-containing compounds is rapidly increasing.

There is a large amount of lithium and the like on the earth. However, areas where lithium and the like are buried underground are uneven. On the other hand, lithium and the like are contained in large amounts in seawater, and the content of lithium and the like in seawater is enormous relative to the reserves of lithium and the like in the ground. Further, lithium and the like are also included in “Nigari” used for making tofu, an electrolyte for a used lithium ion battery, a concentrated solution discharged during desalination of seawater, and the like. However, each lithium-containing liquid such as seawater, bittern, an electrolytic solution, and a concentrated solution contains not only lithium (ion) but also other metals (ions) such as potassium, sodium, and calcium. Therefore, in order to recover lithium and the like from the above-described lithium-containing liquid, a membrane for separating lithium ions from other metal ions (hereinafter, referred to as a lithium ion separation membrane) is being developed.

For example, in Patent Literature 1, resin particles and solid electrolyte particles having lithium ion conductivity are arranged in one layer on the same surface, and heated to a temperature equal to or higher than the melting point of the resin to form a part of the solid electrolyte particles into a film. The film exposed on both sides is described. This film is said to be capable of selectively transmitting lithium ions. In addition, although the required properties are different from those of the lithium ion separation membrane, a sheet that conducts lithium ions includes a solid electrolyte sheet applied to the production of a solid electrolyte layer of a solid secondary battery. For example, Patent Literature 2 discloses that a composition obtained by dispersing a solid electrolyte having lithium ion conductivity and a binder in a dispersion medium containing a fluorine-based solvent is coated on a substrate, and heat-treated. The solid electrolyte sheet obtained by the above method is described.

JP-A-2017-216066 JP 2010-146823 A

A membrane that selectively permeates lithium ions (hereinafter, referred to as a “lithium ion selective permeation membrane”) is used to quickly recover lithium ions (hereinafter, also referred to as “Li ⁺ ”) with higher selectivity. Characteristics are required. Further, it is desirable that the lithium ion selective permeable membrane be capable of maintaining the shape of the membrane by binding lithium ion conductors to each other, that is, to have a film-forming property. With the above film forming property, the gap between the lithium ion conductors can be reduced (for example, the distance between the lithium ion conductors can be reduced), so that the permeability of lithium ions per unit film area can be improved. It is possible. However, the membrane described in Patent Literature 1 and the sheet described in Patent Literature 2 are intended to prepare membranes and sheets excellent in lithium ion selectivity and lithium ion selectivity and recovery rate (recovery rate), which are necessary properties as a lithium ion selective permeable membrane. , The film formability is inferior.

INDUSTRIAL APPLICABILITY The present invention has excellent lithium ion selectivity and excellent lithium ion selectivity and recovery rate (hereinafter, these two properties are collectively referred to as "Li ⁺ selective properties"). It is an object to provide a membrane. It is another object of the present invention to provide a lithium ion recovery device, a lithium-containing compound recovery device, and a lithium ion recovery method that are excellent in Li ⁺ selection characteristics.

In view of the above problems, the present inventors have conducted intensive studies and have found that a combination of a lithium ion conductor (A) and a polymer (B) having a specific structural unit having an anionic group having a lithium ion as a counter cation is combined. It has been found that when used, a film can be formed, and the obtained film is excellent in the above-described film forming properties and Li ⁺ selectivity. The present invention has been further studied based on these findings, and has been completed.

The above problem has been solved by the following means.

<1>

A selectively permeable lithium ion membrane comprising a lithium ion conductor (A) and a polymer (B) having a structural unit represented by the following general formula (B1).

In the above formula, L ¹ and L ² each independently represent an alkylene group which may have a substituent, R ¹ to R ³ each independently represent a hydrogen atom or an alkyl group, and A represents —NR ⁴ − , —O— or —S—, R ⁴ represents a hydrogen atom or an alkyl group, and Y ^B1 represents an anionic group having a lithium ion as a counter ion. * Indicates a binding site as a structural unit of the polymer.

<2>

The lithium ion selective permeable membrane according to <1>, wherein the structural unit represented by the general formula (B1) has an SP value of 14 or more and 24 or less.

<3>

The lithium ion selective permeable membrane according to <1> or <2>, wherein the structural unit represented by the general formula (B1) is a structural unit represented by the following general formula (B2).

In the above formula, L ²¹ and L ²² each independently represent an alkylene group having 1 to 7 carbon atoms, R ²¹ to R ²³ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Y ^B2 represents It has the same ^meaning as YB1 described above. * Indicates a binding site as a structural unit of the polymer.

<4>

The anionic group is _-SO ³ - is a ^{Li +, <1> ~ <} 3> lithium ion permselective membrane according to any one of.

<5>

A water-insoluble polymer (C) different from the polymer (B), wherein at least one of a cyano group, an amide group, an amino group, a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond And the water-insoluble polymer (C) having a glass transition temperature of 0 ° C. or lower, wherein the lithium ion selective permeable membrane according to any one of <1> to <4>.

<6>

A lithium ion recovery device having the lithium ion selective permeable membrane according to any one of <1> to <5>.

<7>

A lithium-containing compound recovery device comprising the lithium ion recovery device according to <6>.

<8>

A method for recovering lithium ions, comprising recovering lithium ions using the lithium ion selective permeable membrane according to any one of <1> to <5>.

In this specification, unless otherwise specified, when there are a plurality of substituents, linking groups, structural units, and the like (hereinafter, referred to as substituents) represented by a specific code or formula, or when a plurality of Alternatively, when they are alternatively specified, the respective substituents and the like may be the same or different from each other. This holds true for the definition of the number of substituents and the like.

In the present specification, the “group” of each group described as an example of each substituent is used to mean both an unsubstituted form and a form having a substituent. For example, “alkyl group” means an alkyl group which may have a substituent. Further, when the number of carbon atoms of the group is limited, the number of carbon atoms of the group means the total number of carbon atoms including the substituent unless otherwise specified.

In the present invention, the term “compound” is used to include not only the compound itself but also its salt and its ion. Also, it is meant to include a structure in which a part of the structure is changed, as long as the effects of the present invention are not impaired. Further, a compound that is not specified to be substituted or unsubstituted may have any substituent within a range that does not impair the effects of the present invention. This is the same for the substituent and the linking group.

In this specification, “(meth) acrylate” is used to mean both acrylate and methacrylate. The same applies to “(meth) acrylic acid”, “(meth) acrylamide”, “(meth) acrylonitrile” and “(meth) acryloyl group”.

In this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

In the present specification, the SP value is described by omitting the unit (cal / cm ³ ) ^1/2 .

The lithium ion permselective membrane of the present invention is excellent in film-forming properties, and is also excellent in lithium ion selectivity and recovery rate (Li ⁺ selectivity). Further, the lithium ion recovery device, the lithium-containing compound recovery device, and the lithium ion recovery method of the present invention enable lithium ions or lithium-containing compounds to be recovered at an excellent recovery rate and an excellent selectivity. .

FIG. 1 is a schematic diagram of a lithium ion recovery device according to one embodiment of the present invention. FIG. 2 is a schematic diagram of a lithium-containing compound recovery device according to one embodiment of the present invention.

<Lithium ion selective permeable membrane>

The lithium ion selective permeable membrane of the present invention is a lithium ion conductor (A) and a polymer (B) having a structural unit represented by the following general formula (B1) (hereinafter, also simply referred to as “polymer (B)”). ). The form of the lithium ion selective permeable membrane of the present invention may be any form that has film-forming properties and has lithium ion conductivity. Both the lithium ion conductor (A) and the polymer (B) constituting the lithium ion selective permeable membrane of the present invention have lithium ion conductivity. Therefore, one form of the membrane includes a form in which the lithium ion conductor (A) is dispersed in the polymer (B) (for example, a form of a composite film). This variance may be random, regular, or the like.

The lithium ion selective permeable membrane of the present invention having the above-described configuration is excellent in film forming property, lithium ion selectivity and recovery rate. The reason for this is not clear, but is presumed as follows.

The polymer (B) is formed by linking an anionic group having a lithium ion (hereinafter also referred to as “Li ⁺ ”) as a counter cation to a linking group having a specific chain length or more represented by —L ¹ -AL ² —. And has a specific structural unit having a carbon chain. Since the polymer (B) has the anionic group, in the lithium ion selective permeable membrane of the present invention, the lithium ion conductor (A) having a high lithium ion selectivity is dispersed in the polymer (B) in the state where the ion conductivity is high. The body (A) and the polymer (B) interact with each other to sufficiently bind the lithium ion conductors (A) to each other, and further to improve the adhesion between the lithium ion conductor (A) and the polymer (B). Can be increased, and it is considered that excellent film-forming properties are exhibited. In addition, since the anionic group in the polymer (B) is bonded to the carbon chain via a linking group having a specific length or more as described above, the polymer has an appropriate mobility. Therefore, the polymer (B) not only does not inhibit the ionic conductivity of the coexisting lithium ion conductor (A) but also reinforces the lithium ion conductivity of the lithium ion conductor (A) by its own lithium ion conductivity. . As a result, it is considered that the lithium ion selective permeable membrane of the present invention has enhanced lithium ion permeability and exhibits an excellent lithium ion recovery rate.

The thickness of the lithium ion selective permeable membrane of the present invention can be appropriately selected according to the intended mode, the size of the device to be incorporated, and the like. For example, it is 1 to 1000 μm, and may be 10 to 500 μm.

The lithium ion selective permeable membrane of the present invention may be in a form having a support and a substrate. Since the lithium ion selective permeable membrane of the present invention has excellent film-forming properties, it can be handled alone without using a support or a substrate.

When incorporating the lithium ion selective permeable membrane of the present invention into a lithium ion recovery device or a lithium-containing compound recovery device, the membrane area can be appropriately selected depending on the intended mode, the size of the device to be incorporated, and the like. . For example, it is 0.5 to 500,000 cm ² and may be 1 to 100,000 cm ² .

(Lithium ion conductor (A))

The lithium ion conductor (A) used in the present invention is a compound exhibiting lithium ion conductivity (conducts lithium ions and does not easily conduct other metal ions such as potassium and sodium (preferably does not conduct)). If it is, there is no particular limitation. Further, the lithium ion conductor (A) preferably has resistance to a lithium-containing liquid and a recovery liquid described later (for example, “water-insoluble” described later). Specific examples of the lithium ion conductor (A) include an oxide-based inorganic solid electrolyte. The oxide-based inorganic solid electrolyte is preferably a compound containing an oxygen atom and having lithium ion conductivity.

Since the lithium ion conductor (A) used in the present invention is a solid in a steady state, it is generally not dissociated or released into cations and anions. In this regard, it is clearly distinguished from water or lithium salts, in which cations and anions are dissociated or free in the polymer. That is, the lithium ion conductor (A) is used in the sense that it does not contain a lithium salt. Here, the lithium salt refers to a low-molecular weight inorganic or organic lithium salt compound (for example, CF ₃ SO ₃ Li used in Test No. c11 in Examples described later).

Specific examples of the compound include, for example, Li _xa La _ya TiO ₃ [xa = 0.3 to 0.7, ya = 0.3 to 0.7] (LLT), Li _xb La _yb Zr _zb M ^bb _mb O _nb (M ^bb is at least one element of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, Sn, xb satisfies 5 ≦ xb ≦ 10, and yb satisfies 1 ≦ yb Satisfies ≦ 4, zb satisfies 1 ≦ zb ≦ 4, mb satisfies 0 ≦ mb ≦ 2, nb satisfies 5 ≦ nb ≦ 20), Li _xc _Byc M ^cc _zc O _nc (M ^cc is Xc satisfies 0 <xc ≦ 5, yc satisfies 0 <yc ≦ 1, and zc satisfies 0 <zc ≦ C, S, Al, Si, Ga, Ge, In and Sn. met 1, nc satisfies 0 <nc ≦ 6.), Li xd ( _{_{l, Ga) yd (Ti,}} Ge) zd Si ad P md O nd ( provided that, 1 ≦ xd ≦ 3,0 ≦ yd ≦ 1,0 ≦ zd ≦ 2,0 ≦ ad ≦ 1,1 ≦ md ≦ 7, _{^{3 ≦ nd ≦ 13), Li}} (3-2xe) M ee xe D ee O (xe represents a number of 0 to ^0.1, ^{.D ee} ^{M ee} is representative of a divalent metal atom is a halogen atom or Represents a combination of two or more halogen atoms.), Li _xf Si _yf O _zf (1 ≦ xf ≦ 5, 0 <yf ≦ 3, 1 ≦ zf ≦ 10), Li _xg S _yg O _zg (1 ≦ xg ≦ 3, 0 <yg ≦ 2, 1 ≦ zg ≦ 10), Li ₃ BO ₃ —Li ₂ SO ₄ , Li ₂ O—B ₂ O ₃ —P ₂ O ₅ , Li ₂ O—SiO ₂ , Li ₆ BaLa ₂ _{_{_{_{ta 2 O 12, Li 3 PO}}}} (4-3 / 2w) N w (w is w <1), LI ICON (Lithium super ionic conductor) type _Li 3.5 _Zn 0.25 GeO ₄ having a crystal structure, _La 0.55 _Li 0.35 _TiO 3 having a perovskite crystal structure, NASICON (Natrium super ionic conductor) type crystal structure LiTi ₂ P ₃ O ₁₂ , Li _{1 + xh + yh} (Al, Ga) _xh (Ti, Ge) _2-xh Si _yh P _3-yh O ₁₂ (where 0 ≦ xh ≦ 1, 0 ≦ yh ≦ 1), garnet Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) having a type crystal structure is exemplified. Further, a phosphorus compound containing Li, P and O is also desirable. For example, lithium phosphate (Li ₃ PO ₄ ), LiPON in which a part of oxygen of lithium phosphate is substituted by nitrogen, LiPOD ¹ (D ¹ is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr , Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc.). Further, LiA ¹ ON (A ¹ is at least one of Si, B, Ge, Al, C, Ga, and the like) and the like can also be preferably used.

The lithium ion conductor (A) is preferably a particle. In this case, the median diameter D50 of the lithium ion conductor particles is not particularly limited, but is preferably 30 μm or less, more preferably 20 μm or less, and more preferably 15 μm or less, in order to improve the film strength. preferable. The lower limit is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.6 μm or more.

The lithium ion conductor (A) preferably has a form in which the particle size does not largely change before and after the formation of the lithium ion selective permeable membrane, and is dispersed in the polymer (B) after the film is formed. Therefore, it is preferable to use the particulate lithium ion conductor (A) as a raw material for forming the lithium ion selective permeable membrane.

The measurement of the average particle diameter of the particles of the lithium ion conductor (A) is performed according to the following procedure. The lithium ion conductor particles are diluted with 1% by weight of a dispersion of 1% by mass in a 20 mL sample bottle using heptane. The dispersion sample after dilution is irradiated with 1 kHz ultrasonic wave for 10 minutes and used immediately after the test. Using this dispersion liquid sample, data was taken 50 times at a temperature of 25 ° C. using a laser diffraction / scattering type particle size distribution analyzer LA-920 (trade name, manufactured by HORIBA) using a quartz cell for measurement. Obtain the volume average particle size. For other detailed conditions, refer to the description of JIS Z 8828: 2013 “Particle size analysis-dynamic light scattering method” as necessary. Five samples are prepared for each level, and the average value is adopted.

The lithium ion selective permeable membrane of the present invention may contain one type of lithium ion conductor (A), or may contain two or more types.

The content of the lithium ion conductor (A) in the lithium ion selective permeable membrane of the present invention is preferably 20% by mass or more, and more preferably 30% by mass in the total solid content in order to improve the recovery rate and selectivity of lithium ions. The above is more preferable, and 40% by mass or more is further preferable. The upper limit is preferably 90% by mass or less, and more preferably 80% by mass or less, from the viewpoint of film formability.

In the present invention, the solid content refers to a component remaining in the film when a lithium ion selective permeable membrane is formed by drying by blowing air at 50 ° C. for 5 hours and vacuum drying at 100 ° C. for 5 hours, specifically, a solvent described below. Means other components.

(Polymer having structural unit represented by formula (B))

The polymer having a structural unit represented by the following general formula (B) is a polymer in which the counter cation in the anionic group is a hydrogen atom or an alkali metal ion, and the lithium cation of the present invention in which the counter cation is limited to lithium ion. It includes a polymer (B) which is a constituent material of the permselective membrane and a polymer (b) in which the counter cation is limited to sodium ion or potassium ion.

The type of the polymer having the structural unit represented by the following general formula (B) is not particularly limited as long as it has the following structural unit, but the polymer has high flexibility and can achieve the above-described effects at a high level. In this respect, (hydrogenated) aliphatic hydrocarbon polymers and the like are preferable, and (hydrogenated) aliphatic acyclic hydrocarbon polymers are more preferable.

The aliphatic hydrocarbon polymer and the aliphatic acyclic hydrocarbon polymer may be saturated or unsaturated, and preferably have a polymer main chain mainly formed of carbon-carbon bonds. For example, a diene-based polymer having a double bond in the main chain and a non-diene-based polymer having no double bond in the main chain are exemplified. Specific examples thereof include polybutadiene, polyisoprene, butyl rubber, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, or a hydrogen reduced product of an aromatic hydrocarbon polymer described later. Can be

In the above formula, L ¹ and L ² each independently represent an alkylene group which may have a substituent, R ¹ to R ³ each independently represent a hydrogen atom or an alkyl group, and A represents —NR ⁴ − , -O- or -S-, R ⁴ represents a hydrogen atom or an alkyl group, and Y ^B represents an anion having a hydrogen atom or an alkali metal ion (preferably a lithium ion, a sodium ion or a potassium ion) as a counter ion. Represents a functional group. * Indicates a binding site as a structural unit of the polymer.

In the present invention, the anionic group may be any group that can form an anion and impart lithium ion conductivity to the polymer itself. Such anionic _{groups, -C (= O) OM,} -S (= O) 2 OM, -OS (= O) 2 OM, -P (= O) (OM) 2 or -OP (= O) (OM) _{2 and the} like.

M represents a hydrogen atom or an alkali metal ion. In the selectively permeable lithium ion membrane of the present invention, the M may be separated (free) or not separated (free). M is a lithium ion in the polymer (B) which is a constituent material of the lithium ion selective permeable membrane, and is a hydrogen atom or an alkali metal ion excluding the lithium ion in the polymer (b).

The anionic group is preferably —C (＝ O) OM or —S (＝ O) ₂ OM, and —S (＝ O) ₂ having a large ion dissociation constant from the viewpoint of obtaining a better lithium ion recovery rate. OM is preferred.

The polymer, in the structural unit represented by the above formula (B), may have a Y ^B except Meikisuru Y ^B in the formula.

For each substituent group other than Y ^B, hereinafter described polymer (B) is a structural material of a lithium ion selective permeable membrane of the present invention.

(Polymer (B))

-Structural unit represented by formula (B1)-

The polymer (B) used in the present invention has a structural unit represented by the following general formula (B1). This polymer (B) has lithium ion conductivity.

In the above formula, L ¹ and L ² each independently represent an alkylene group which may have a substituent. The carbon number of the alkylene group which may have a substituent in L ¹ is preferably 1 to 10, more preferably 1 to 7, still more preferably 1 to 5, particularly preferably 1 to 3, and 1 or 2 Most preferred. The number of carbon atoms of the alkylene group which may have a substituent in L ² is preferably 1 to 10, more preferably from 1 to 7, more preferably 1 to 5, and most preferably 1-3.

The L ¹ and L ² substituents which may have is not particularly limited as long as it does not impair the effects of the present invention, such as hydroxy group, and oxo group (= O) or Y ^B1.

The alkylene group which may have a substituent in L ¹ and L ² may be linear or branched, and may have a ring structure (for example, a 5- or 6-membered ring structure, The ring-constituting atom is preferably a carbon atom.). When L ¹ and L ² are an alkylene group having a ring structure, the bond constituting the ring structure is a group represented by -L ¹ -AL ² -from the viewpoint of not impairing the mobility of the anionic group. Of these, it is preferable that the atom is not in the following shortest chain, and it is more preferable that one of the atoms forming the ring structure be present as a quaternary carbon atom in the shortest chain.

R ¹ to R ³ each independently represent a hydrogen atom or an alkyl group. The alkyl group in R ¹ to R ³ preferably has 1 to 4 carbon atoms, more preferably 1 or 2, and still more preferably 1. R ¹ is preferably a hydrogen atom or methyl, and more preferably a hydrogen atom. Each of R ² and R ³ is preferably a hydrogen atom.

A ^-NR 4 is -, - O-or -S- shown, ^{R 4} represents a hydrogen atom or an alkyl group. As the alkyl group for R ⁴ , the description of the alkyl group for R ¹ to R ³ can be preferably applied. R ⁴ is more preferably a hydrogen atom.

A is preferably -O- or -S-, and more preferably -S-.

Y ^B1 represents an anionic group having a lithium ion as a counter cation. As for preferable anionic groups, the description of the above-described anionic groups can be applied.

* Indicates a binding site as a structural unit of the polymer.

In the structural unit represented by the general formula (B1), the chain connecting the carbon atom to which R ¹ is bonded and the anionic group Y ^B1 is too long in consideration of the ratio of the anionic group in the polymer (B). Preferably not. Specifically, among the groups represented by -L ¹ -AL ^2- , the number of bonds of atoms constituting the shortest chain (hereinafter, also simply referred to as "the shortest atom number") is preferably 10 or less, and 8 or less. The following is more preferable, the value of 7 or less is further preferable, and the value of 6 or less is most preferable. The lower limit of the minimum number of atoms is 3 or more, preferably 4 or more, more preferably 5 or more from the viewpoint of imparting mobility to the anionic group to increase the permeability of lithium ions and exhibit an excellent lithium ion recovery rate. More preferred.

For example, in the structural unit represented by the general formula (B1) in the polymer (P1-1) in the examples, two carbon atoms in the ethylene group, one sulfur atom and three carbon atoms in the propylene group are used. A total of 6 is the shortest atom number.

Further, the side chain when the shortest chain is regarded as the main chain, that is, the number of bonds of atoms constituting the longest chain among the branched chains in L ¹ and L ² (hereinafter, also simply referred to as “longest atom number”). ) Is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less.

The upper limit of the SP value of the structural unit represented by the general formula (B1) improves the hydrophobicity of the structural unit having an anionic group, suppresses the permeation of hydrated ions, and increases the water permeability of the lithium ion selective membrane. In respect of suppression, 24 or less is preferable, and 22 or less is more preferable. The lower limit of the SP value is preferably 14 or more, more preferably 16 or more. That is, the SP value is preferably from 14 to 24, and more preferably from 16 to 22.

The SP value of the structural unit represented by the general formula (B1) is determined as follows.

[SP value calculation method]

"SP value" as used herein is a value determined by calculation using the ^{HSPiP 5 th Edition 5.0.04 (https://hansen-solubility.com/downloads.php)} . In calculating the polymer structure, the calculation is made by setting both ends of the repeating unit structure to *.

-Structural unit represented by formula (B2)-

The structural unit represented by the general formula (B1) is preferably a structural unit represented by the following general formula (B2).

In the above formula, L ²¹ and L ²² each independently represent an alkylene group having 1 to 7 carbon atoms. The carbon number of the alkylene group in L ²¹ is preferably 1 to 5, more preferably 1 to 3, and still more preferably 1 or 2. The alkylene group in L ²² is preferably 1 to 5, 1 to 3 more preferred.

As the alkylene group having 1 to 7 carbon atoms in L ²¹ and L ²² , description other than the carbon number of the alkylene group which may have a substituent in L ¹ and L ² can be preferably applied.

R ²¹ to R ²³ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The number of carbon atoms of the alkyl group in R ²¹ to R ²³ is preferably 1 or 2, more preferably 1. R ²¹ is preferably a hydrogen atom or methyl, and more preferably a hydrogen atom. Each of R ²² and R ²³ is preferably a hydrogen atom.

Y ^B2 has the same meaning as Y ^B1 in Formula (B1), and represents an anionic group having a lithium ion as a counter cation. As for preferable anionic groups, the description of the above-described anionic groups can be applied.

* Indicates a binding site as a structural unit of the polymer.

-L 21 ^-S-L 22 ^- Of the groups represented, coupled atoms of the atoms that constitute the shortest chain (. Hereinafter, simply also referred to as "shortest number atoms") is preferably 3-10. The shortest number of atoms and the side chain when the shortest chain is regarded as the main chain, that is, the bond number of the atoms constituting the longest chain among the branched chains in L ²¹ and L ²² (hereinafter simply referred to as the “longest atom number The description of the shortest atom number and the longest atom number in the group represented by -L ¹ -AL ² -in the general formula (B1) can be preferably applied.

-Structural unit represented by formula (b1)-

The polymer (b) having a counter cation in the anionic group different from that of the polymer (B) has a structural unit represented by the following formula (b1).

In the above ^formulas, ^{^{L 1, L 2, R 1}} ~ R 3 and A have the same meanings as ^{^{^{L 1, L 2, R 1}}} ~ R 3 and A in the formula (B1).

Y ^b1 represents an anionic group having a hydrogen atom or an alkali metal ion (preferably a sodium ion or a potassium ion) as a counter ion. However, the lithium ions are not included in the alkali metal ions in the Y ^b1. As for preferable anionic groups, the description of the above-described anionic groups can be applied.

* Indicates a binding site as a structural unit of the polymer.

Examples of the structural units represented by the general formulas (B), (B1) and (b1) include the following structural units. However, it is not limited to these structural units.

In the following chemical structural formula, M represents a hydrogen atom or an alkali metal ion, and corresponds to the counter cation defined by the formulas (B), (B1) and (b1). As the anionic group of the following chemical structural formula, -COOM or -SO ₃ M is shown, but a structure in which -P (= O) (OM) ₂ or -OP (= O) (OM) ₂ is also exemplified. . * Indicates a binding site as a structural unit of the polymer.

The polymer (B) may have a structural unit other than the structural unit represented by the general formula (B1) (hereinafter, referred to as other structural units). Other structural units are not particularly limited as long as they are copolymerizable with the structural unit represented by the general formula (B1). Preferably, a structural unit capable of forming the above-mentioned aliphatic hydrocarbon polymer is mentioned, and specifically, ethylene, 1,3-butadiene, isobutylene, isoprene, acrylonitrile, 5-ethylidene-2-norbornene, dicyclopentadiene And structural units containing 1,4-hexadiene and the like as monomer components, and oxidized and hydrogenated forms of these structural units.

Like the polymer (B), the polymer (b) may have a structural unit other than the structural unit represented by the general formula (b1). The structural units to be described are mentioned.

The ratio of the structural unit represented by the general formula (B1) and the ratio of the structural unit represented by the general formula (B2) in the polymer (B) are not particularly limited, but are preferably from 5 to 95 mol%, preferably from 10 to 95 mol%. ９０90 mol% is more preferable, and 20-80 mol% is still more preferable.

The ratio of the other structural units in the polymer (B) is not particularly limited, but is preferably from 5 to 95 mol%, more preferably from 10 to 90 mol%, even more preferably from 20 to 80 mol%.

The proportion of the structural unit represented by the general formula (b1) in the polymer (b) is not particularly limited, but is preferably 5 to 100 mol%, more preferably 10 to 90 mol%, and further preferably 20 to 80 mol%.

The ratio of the other structural units in the polymer (b) is not particularly limited, but is preferably 0 to 95 mol%, more preferably 10 to 90 mol%, and further preferably 20 to 80 mol%.

The polymer (B) may independently have one type of the structural unit represented by the general formula (B1) and the other structural units, or may have two or more types.

The polymer (b) may have one or two or more types of the structural unit represented by the general formula (b1) and the other structural units independently.

The form of the polymer (B) and the polymer (b) is not particularly limited, and may be any form such as random, block, and graft as long as the effects of the present invention are not impaired.

The polymers (B) and (b) are different from the above-mentioned lithium salts in that they are polymers having a repeating structural unit. From the above point, the number average molecular weight (Mn) of the polymers (B) and (b) is preferably 800 or more, more preferably 1,000 or more, further preferably 1,000 to 10,000, and particularly preferably 1500 to 8,000. By setting the number average molecular weight within the above preferable numerical range, film formability can be improved. The number average molecular weight can be measured by a known method using gel permeation chromatography (GPC).

The lithium ion selective permeable membrane of the present invention may contain one kind of polymer (B) or two or more kinds.

The content of the polymer (B) in the selectively permeable membrane for lithium ion of the present invention is preferably 5 to 50% by mass, more preferably 7 to 40% by mass, and still more preferably 10 to 30% by mass based on the total solid content. , 15 to 25% by mass.

The terminal structure of the polymer (B) and the polymer (b) is not particularly limited, and depends on the presence or absence of other structural units, the type of a substrate used during synthesis, or the type of a quenching agent (reaction terminator) during synthesis. Not uniquely determined. The terminal structure is, for example, a hydrogen atom, a hydroxy group, a halogen atom, an ethylenically unsaturated group, an alkyl group, an aromatic heterocyclic group (preferably a thiophene ring) or an aromatic hydrocarbon group (preferably a benzene ring). ).

Method for synthesizing polymer (B)

As a method for synthesizing the polymer (B), a polymer having a reactive group a is reacted with a compound having a reactive group b capable of forming a bond by reacting with the reactive group a and an anionic group to form an anion. And a method of polymerizing a monomer having an anionic group to obtain a polymer. In these methods, the anionic group means an anionic group having a lithium ion as a counter cation.

The reactive group a and the reactive group b are groups capable of forming a linking group represented by -L ¹ -AL ² -or a part thereof by a chemical reaction. In order to form a linking group or a partial structure thereof, it can be appropriately selected.

The compound having an anionic group and the monomer having an anionic group used in these synthesis methods can be synthesized by a conventional method without any particular limitation. For example, a conventional ion exchange (lithium such as LiOH) A base or an ion exchange membrane is brought into contact with a compound or monomer having an anionic group having a sodium ion or the like as a counter cation, etc.). As for other reaction conditions, a commonly used method can be appropriately selected.

The method for synthesizing the polymer itself can be a commonly used method, for example, a radical polymerization can be mentioned, and a polymerization initiator, a reaction terminator, and the like are also usually used in combination with the monomers, oligomers, and the like to be used. Agents can be used as appropriate. In addition, a commercially available polymer can also be used as the polymer.

(Water-insoluble polymer (C))

From the viewpoint of imparting excellent membrane strength to the lithium ion selective permeable membrane of the present invention, the lithium ion selective permeable membrane of the present invention also preferably contains a water-insoluble polymer (C). The water-insoluble polymer (C) has one or more of a cyano group, an amide group, an amino group, a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond, and has a glass transition temperature ( Hereinafter, the polymer is also referred to as Tg). The polymer (C) is different from the polymer (B) in that it does not have an anionic group via a linking group having a specific chain length or more represented by -L ¹ -AL ^2-. Water-insoluble polymer).

The water-insoluble in the water-insoluble polymer (C) means that the solubility of the polymer in 100 g of water is 0.1 g or less under the condition of a liquid temperature of 25 ° C.

The water-insoluble polymer (C) may be any of a chain polymerizable polymer, a polyaddition polymer and a polycondensation polymer, and is preferably a chain polymerizable polymer and a polyaddition polymer. Hereinafter, the water-insoluble polymer (C) that is a chain-polymerized polymer is referred to as “chain-polymerized polymer (C)”, and the water-insoluble polymer (C) that is a polyaddition-type polymer is referred to as “polyaddition-type polymer (C)”. ".

-Chain polymerization type polymer (C)-

The chain polymerization type polymer (C) is a polymer obtained by chain-polymerizing one or more monomers having a non-aromatic carbon-carbon double bond. For example, a vinyl polymer is mentioned, and more specifically, a (meth) acrylic polymer and a hydrocarbon polymer (aliphatic hydrocarbon polymer and aromatic hydrocarbon polymer) are mentioned. Examples of the aliphatic hydrocarbon polymer include those described above for the polymer (B). Examples of the aromatic hydrocarbon polymer include polymers having a structural unit derived from an aromatic vinyl compound such as a styrene compound, for example, styrene-butadiene copolymer. Coalescence.

In the synthesis of the chain polymerization type polymer (C), a monomer (monomer (a1)) for introducing any one of a cyano group, an amide group, an amino group, a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond Specific examples of ()) include (meth) acrylonitrile, hydroxy group-containing (meth) acrylate (for example, hydroxyethyl (meth) acrylate), sulfanyl group-containing (meth) acrylate (for example, sulfanylethyl (meth) acrylate), and (meth) Examples thereof include acrylamide, vinyl alcohol, allylamine, and sulfide bond-containing (meth) acrylates (eg, 2-methylthioethyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate). Of these, acrylonitrile and acrylamide are preferred, and acrylonitrile is most preferred. The monomer (a1) may be used alone or in combination of two or more.

In the synthesis of the chain polymerization type polymer (C), a copolymerization component is introduced into a structural unit having any one of a cyano group, an amide group, an amino group, a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond. Examples of the monomer (monomer (b1)) include 1,3-butadiene, isoprene, and alkyl (meth) acrylate (preferably, ethyl acrylate, butyl acrylate, and (2-ethylhexyl) acrylate). Of these, 1,3-butadiene, isoprene or butyl acrylate is preferred, and 1,3-butadiene or isoprene is more preferred. One kind of the monomer (b1) may be used alone, or two or more kinds may be used.

It is also preferable to introduce an ether bond or the like by subjecting a natural rubber containing polyisoprene or the like to epoxidation or the like.

The chain polymerization type polymer (C) may use a third monomer (a monomer other than the above) to such an extent that its function is not impaired.

Among all the structural units derived from the monomers constituting the chain polymerization type polymer (C), the content of the structural unit derived from the monomer (a1) is preferably 26% by mass or more, and the upper limit is preferably 70% by mass or less, and 60% by mass. Is more preferably, and particularly preferably 50% by mass or less. In the case of the chain polymerizable polymer (C) synthesized by epoxidation of natural rubber containing the above polyisoprene or the like, structural units having an ether bond or the like in all structural units constituting the chain polymerizable polymer (C) Is preferably 26% by mass or more, and the upper limit is preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

The chain polymerization type polymer (C) is preferably a polymer synthesized using one kind of the monomer (a1) and one kind of the monomer (b1) from the viewpoint of film strength.

-Polyaddition polymer (C)-

Examples of the polyaddition polymer (C) include polyurethane and polyurea.

Specific examples of monomers for introducing any one of a cyano group, an amide group, an amino group, a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond into the polyaddition polymer (C) include 4,4 4'-methylenebis (phenylisocyanate), 4,4'-methylenebis (cyclohexylisocyanate), isophorone diisocyanate, ethylene glycol, di (propylene glycol) and tetramethylene glycol, or a monomer such as cyano group, amide group, amino group And a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond.

The lower limit of the Tg of the water-insoluble polymer (C) is practically −60 ° C. or higher, and preferably −40 ° C. or higher.

The Tg of the water-insoluble polymer (C) itself can be adjusted by the type of the monomer and the amount used in the synthesis. The form of the water-insoluble polymer (C) is not particularly limited, and includes forms that each of the above polymers can take among random, block, and graft.

The Tg of the water-insoluble polymer (C) is determined as follows.

[Glass-transition temperature]

Using a differential scanning calorimeter (DSC), about 10 mg of the sample (water-insoluble polymer (C)) was cooled from 30 ° C. under a nitrogen atmosphere to −50 ° C. at a temperature lowering rate of 50 ° C./min. Hold for a minute. The temperature is raised from −50 ° C. to 100 ° C. at a rate of 10 ° C./min, and kept at that temperature for 5 minutes. Further, the temperature is lowered to −50 ° C. at a cooling rate of 50 ° C./min, kept at that temperature for 15 minutes, and then raised to 100 ° C. at a heating rate of 10 ° C./min.

The glass transition temperature (Tg) is sensed at the time of the second temperature increase in such a manner that the DSC curve is bent due to a change in specific heat and the base line moves in parallel. The temperature at the intersection of the tangent to the base line at a temperature lower than this bend and the tangent to the point where the slope is maximum at the bent portion is defined as the glass transition temperature (Tg).

In the literature values and catalog values, for polymers deviating from the threshold value of 0 ° C. in the present invention of 40 ° C. or more, those values are adopted. For a polymer having no data or a polymer having a temperature around 0 ° C., the measurement is performed by the above method.

The lithium ion selective permeable membrane of the present invention may contain one type of water-insoluble polymer (C), or may contain two or more types.

The content of the water-insoluble polymer (C) in the lithium ion selective permeable membrane of the present invention is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. The lower limit is preferably 1% by mass or more, and more preferably 5% by mass or more.

The lithium ion selective permeable membrane of the present invention may contain components other than the above-mentioned lithium ion conductor (A), polymer (B) and water-insoluble polymer (C) as long as the effects of the present invention are not impaired. Such components include, for example, ionic liquids described in WO 2017/199821.

-Manufacturing method of lithium ion selective permeable membrane-

The method for producing the lithium ion selective permeable membrane of the present invention is not particularly limited. For example, the lithium ion conductor (A), the polymer (B) and the solvent are stirred for 1 to 5 hours in a temperature range from 20 ° C. to the boiling point of the solvent, and the mixture of the lithium ion conductor (A) and the polymer (B) is stirred. Get. This mixture is applied by a usual method and dried at 40 to 100 ° C. for 3 to 24 hours to obtain the lithium ion selective permeable membrane of the present invention as a membrane.

The solvent is not particularly limited, but a solvent having an SP value of 15 or more is preferable. Specific examples of the solvent include water, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, ethyl acetate, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, chloroform, and dichloromethane. Among them, water, tetrahydrofuran, methyl ethyl ketone, dimethylacetamide, dimethylformamide and N-methyl-2-pyrrolidone are preferred. One type of solvent may be used, or two or more types may be used.

Hereinafter, the lithium ion recovery device, the lithium-containing compound recovery device, and the lithium ion recovery method of the present invention will be described.

<Lithium ion recovery device>

The lithium ion recovery device of the present invention includes the lithium ion selective permeable membrane of the present invention. This lithium ion recovery device is a device for recovering lithium ions from the above-mentioned lithium-containing liquid, and can suitably carry out the lithium ion recovery method of the present invention described later.

The lithium ion recovery device 1A shown in FIG. 1 will be described below.

The lithium ion recovery device 1A includes a lithium ion selective permeable membrane 10. As shown in FIG. 1, the lithium ion recovery device 1A includes a substantially U-shaped processing tank 2 and a lithium ion selective permeable membrane disposed at the bottom of the processing tank 2 and separating the processing tank 2 into two spaces. 10 is provided. The lithium ion selective permeable membrane 10 is arranged such that its edge is in contact with the inner surface of the bottom portion, and separates the two spaces. In addition, the lithium ion recovery device 1A includes a negative electrode 4 disposed in a space separated from the lithium ion selective permeable membrane 10 in a space facing the lithium ion selective permeable membrane 10 and a lithium ion selective permeable membrane in the other space. It has a permselective membrane 10 and a positive electrode 3 spaced apart and facing each other. The positive electrode 3 and the negative electrode 4 are electrically connected to a negative terminal or a positive terminal of the power supply 16 by lead wires. Further, the processing tank 2 is equipped with a device having a stirring function (stirring device). Specifically, a stirrer 17 disposed in the two isolated spaces in the processing tank 2 and a turntable (a driving unit and a control unit, which are installed below the processing tank 2 and rotate the stirrer 17 respectively). 18).

In the lithium ion recovery device 1A, the undiluted solution 5 containing lithium ions is charged into one space (the space where the positive electrode 3 is disposed) separated by the lithium ion selective permeable membrane 10, and the other space (the negative electrode 4 is disposed). The recovered liquid 6 for recovering lithium ions from the undiluted solution 5 is charged into the space (the space).

As the stock solution 5, a liquid containing other metal ions such as potassium ions and sodium ions in addition to lithium ions is used. Specifically, the above-mentioned lithium-containing liquid such as seawater, concentrated seawater, and bittern is used. The recovery liquid 6 is preferably a liquid that does not contain lithium ions and other metal ions at the stage before the operation as a lithium ion recovery apparatus is started. Specifically, dilute hydrochloric acid and water (preferably pure water) ) Etc. can be used.

The method of recovering lithium ions by the lithium ion recovery device 1A can be performed in the same manner as the method using a normal lithium ion separation membrane, except that the lithium ion selective permeable membrane 10 is used. Specifically, the lithium ion recovery device 1A includes the above-mentioned lithium ion selective permeable membrane 10 so that, as described later, the concentration difference (gradient) of the lithium ions between the stock solution 5 and the recovery solution 6 (both electrodes). The lithium ions (not shown) contained in the stock solution 5 can be selectively transmitted (moved) to the recovery solution 6 quickly and selectively through the lithium ion selective permeable membrane 10 even if no voltage is applied therebetween. Can be. At this time, in addition to the recovery of lithium ions, a current flowing between the electrodes due to the transmission (movement) of lithium ions can be taken out as electric power. That is, it can be used as a battery without applying a voltage to the positive electrode 3 and the negative electrode 4 of the lithium ion recovery device 1A.

On the other hand, the lithium ion recovery device 1A of the present invention can further increase the recovery efficiency of lithium ions by applying a voltage between both electrodes and performing electrodialysis.

As described above, the lithium ion selective permeable membrane of the present invention is used in a lithium ion collecting apparatus, and the lithium ion collecting apparatus including the lithium ion selective permeable membrane of the present invention has an excellent lithium ion collecting speed and It can be recovered with excellent selectivity.

The lithium ion recovery device of the present invention is not limited to the lithium ion recovery device 1A. For example, in the above-described lithium ion recovery device 1A, the processing tank 2 has a substantially U shape, but in the present invention, the shape of the processing tank 2 can be applied without any particular limitation to a generally adopted shape. In addition, the lithium ion recovery device 1A includes a magnetic stirrer as a stirring device. However, in the present invention, a stirring device may not be provided, and a known stirring device other than the magnetic stirrer (for example, a mechanical stirrer, (Shaker) and a circulation mechanism shown in FIG. 2 to be described later. The size, structure, material, and the like of the treatment tank 2, the positive electrode 3, and the negative electrode 4 in the lithium ion recovery device 1A are not particularly limited, and a commonly used configuration can be appropriately selected.

<Lithium-containing compound recovery device>

The lithium-containing compound recovery device of the present invention includes the lithium-ion recovery device of the present invention, and further includes a device that neutralizes the recovered lithium ions to convert the lithium ions into a lithium-containing compound.

Hereinafter, the lithium-containing compound recovery apparatus 100 shown in FIG. 2 will be described as an example, together with the lithium ion recovery method of the present invention.

The lithium-containing compound recovery device 100 shown in FIG. 2 includes a lithium ion recovery device 1B having the lithium ion selective permeable membrane 10 of the present invention. The lithium ion recovery apparatus 1B includes a cylindrical processing tank 2, a lithium ion selective permeable membrane 10 disposed in the processing tank 2, and defining two isolated spaces in the processing tank 2, and a lithium ion selective permeable membrane. A positive electrode 3 is disposed in contact with one surface of the positive electrode 10, and a negative electrode 4 is disposed in contact with the other surface of the lithium ion selective permeable membrane 10. The positive electrode 3 and the negative electrode 4 are connected to the + terminal or the − terminal of the power supply, respectively. The lithium ion selective permeable membrane 10 is provided with a circulation mechanism for circulating the undiluted or recovered liquid as a stirring device. This circulating mechanism can perform not only the function of stirring the stock solution or the recovered solution, but also the function of exchanging or recovering them. Specifically, the stock solution storage tank 11 for storing (storing) the stock solution 5 is connected to the isolated space in which the stock solution storage tank 11 and the positive electrode 3 are arranged, and the stock solution 5 is transferred from the stock solution storage tank 11 to the isolated space. Pipe (stock solution transfer pipe) 13a, a stock solution stock pipe 11b connecting the stock solution storage tank 11 and the isolated space in which the positive electrode 3 is disposed, and discharging the stock solution 5 from the isolated space to the stock solution storage tank 11. , And pumps 14a and 14b provided in the stock solution transfer pipe 13a and the stock solution discharge pipe 13b, respectively. On the other hand, a recovery storage tank 12 that stores (retains) the recovery liquid 6 is connected to an isolated space in which the recovery storage tank 12 and the negative electrode 4 are arranged, and the recovery liquid 6 is transferred from the recovery storage tank 12 to the isolated space. A pipe (collected liquid transfer pipe) for connecting the collected liquid storage tank 12 and the isolated space in which the negative electrode 4 is disposed to discharge the collected liquid 6 from the isolated space to the collected liquid storage tank 12 (collected liquid discharge pipe) 13d), and pumps 14c and 14d provided in the recovered liquid transfer pipe 13c and the recovered liquid discharge pipe 13d, respectively. In addition, a lithium-containing compound recovery unit (tank) 15 is provided in the recovery liquid storage tank 12. The lithium-containing compound recovery unit 15 has a reaction tank that stores the recovery liquid 6 and converts lithium ions into lithium-containing compounds, and further inputs a compound that converts lithium ions into lithium-containing compounds, such as a hopper. (Not shown). This reaction tank is provided with a pipe (collected liquid transfer pipe) 13e extending to the collection storage tank 12, and a pump 14e in the middle of the pipe 13e.

The method of recovering a lithium-containing compound by the lithium-containing compound recovery apparatus 100 is the same as the method of recovering lithium ions by using the lithium ion selective permeable membrane 10 except that the lithium ions recovered using a normal lithium ion separation membrane contain lithium ions. It can be carried out in the same manner as in the method of converting into a compound. Specifically, the stock solution 5 is stored in the stock solution storage tank 11. The undiluted solution 5 is sent by the pump 14a through the pipe 13a to the isolated space of the processing tank 2 where the positive electrode 3 is arranged, and returned to the undiluted solution storage tank 11 by the pump 14b through the pipe 13b. Thus, the stock solution 5 is circulating between the stock solution storage tank 11 and the processing tank 2. On the other hand, the recovery liquid storage tank 12 stores the recovery liquid 6 (dilute hydrochloric acid or the like). The recovered liquid 6 is sent by the pump 14c through the pipe 13c to the isolated space of the processing tank 2 where the negative electrode 4 is disposed, and returned to the recovered liquid storage tank 12 through the pipe 13d by the pump 14d. Thus, the recovery liquid 6 is circulating between the recovery liquid storage tank 12 and the processing tank 2. In the lithium-containing compound recovery apparatus 100, lithium ions (not shown) are recovered in the recovery liquid 6 by the lithium ion recovery apparatus 1B while circulating the stock solution 5 and the recovery liquid 6 as necessary. The method of recovering lithium ions using the lithium ion recovery device 1B is the same as the method of recovering lithium ions using the lithium ion recovery device 1A.

After the lithium ions are recovered in this way and the concentration of lithium ions in the recovery liquid 6 in the recovery liquid storage tank 12 reaches a desired value, the recovery liquid 6 is passed through the pipe 13e by the pump 14e, and is returned to the lithium-containing compound recovery section. 15 In the lithium-containing compound recovery section 15, a compound that converts lithium ions into a lithium-containing compound, for example, an aqueous solution of sodium carbonate (Na ₂ CO ₃ ) is added to the recovery liquid 6, and the lithium-containing compound (Li ₂ CO ₃ ) A precipitate can be obtained. The precipitate is solid-liquid separated by a conventional method, and if necessary, purified and dried to obtain a lithium-containing compound, for example, a powder of Li ₂ CO ₃ .

As described above, the lithium-containing compound recovery device 100 including the lithium-ion recovery device 1B can recover a lithium-containing compound having a high lithium ion purity with high productivity.

The lithium-containing compound recovery device of the present invention is not limited to the lithium-containing compound recovery device 100 described above. For example, in addition to the lithium ion recovery device 1B, the lithium ion recovery device 1A provided in the lithium-containing compound recovery device can be applied to the lithium ion recovery device 1A, and further the above-mentioned changes can be applied.

Regarding the lithium ion recovery device, the lithium-containing compound recovery device, and the lithium ion recovery method, for example, JP-A-2015-34315 and JP-A-5765850 can be referred to as needed.

Hereinafter, the present invention will be described in more detail based on examples. It should be noted that the present invention is not construed as being limited thereto. “Room temperature” means 25 ° C. In the chemical structural formulas described below, * indicates a binding site as a polymer structural unit.

[Example 1]

(1) Synthesis of polymer (B)

[Synthesis Example 1-1] Synthesis of polymer (P1-1)

According to the following scheme, a polymer (P1-1) was synthesized.

Ion exchange of sodium 3-mercapto-1-propanesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.) using Amberlite (registered trademark, ion exchange resin, manufactured by Aldrich), which has been previously Li-substituted with an aqueous solution of lithium acetate, yields 3 -Lithium mercapto-1-propanesulfonate was obtained.

2.4 g of lithium 3-mercapto-1-propanesulfonate and 6.4 g of dimethylacetamide (DMAc) were added to a 50 ml flask, and the mixture was stirred at 60 ° C. for 30 minutes. Thereafter, 1.0 g of NISSO-PB B-1000 (trade name, 1,2-polybutadiene homopolymer, manufactured by Nippon Soda Co., Ltd.) and V-601 (trade name, oil-soluble azo polymerization initiator, Wako Pure Chemical Industries, Ltd.) 1.4 g) and 3.2 g of DMAc were added, and the mixture was stirred under a nitrogen atmosphere at 60 ° C. for 30 minutes, and further at 80 ° C. for 8 hours. After the temperature of the reaction solution was returned to room temperature, the reaction solution was added to 135 g of isopropyl alcohol (IPA), and the precipitate was washed with 135 g of IPA to obtain 1.7 g of a polymer (P1-1). (Mn3700, ratio of structural unit represented by general formula (B1) in polymer: 70 mol%).

[Synthesis Example 1-2] Synthesis of polymer (P1-2)

The following polymer (P1-2) was synthesized in the same manner as in the synthesis of polymer (P1-1) except that lithium 3-mercapto-1-propanesulfonate was changed to the corresponding compound (Mn2900, polymer Of the structural unit represented by the general formula (B1): 70 mol%).

[Synthesis Example 1-3] Synthesis of polymer (P1-3)

In the synthesis of the polymer (P1-1), the following polymer (P1) was prepared in the same manner except that NISSO-PB B-1000 was changed to NISSO-PB JP-100 (trade name, epoxidized polybutadiene, manufactured by Nippon Soda Co., Ltd.). -3) was synthesized (Mn4300, proportion of the structural unit represented by the general formula (B1) in the polymer: 70 mol%)

[Synthesis Example 1-4] Synthesis of polymer (P1-4)

Polymer (P1-4) was synthesized in the same manner as in the synthesis of polymer (P1-1) except that the amount of lithium 3-mercapto-1-propanesulfonate was changed to 0.8 g (Mn3000, polymer (Ratio of the structural unit represented by the general formula (B1) in the above: 50 mol%)

[Synthesis Example 2-1] Synthesis of polymer (P1-5)

According to the following scheme, a polymer (P1-5) was synthesized.

In a 100 ml flask, 0.8 g of lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries), 15 g of water, 15 g of IPA, and 3-aminopropanesulfonic acid (manufactured by Aldrich)

2.5 g was added, and the temperature was raised to 78 ° C. while stirring. Further, 5.0 g of NISSO-PB JP-100 (trade name, epoxidized polybutadiene, manufactured by Nippon Soda Co., Ltd.) was slowly added, and the mixture was reacted at the same temperature for 20 hours. By concentrating the obtained reaction solution, 7.6 g of a polymer (P1-5) was obtained (Mn2200, ratio of the structural unit represented by the general formula (B1) in the polymer: 20 mol%).

[Synthesis Example 2-2] Synthesis of polymer (P1-6)

The following polymer (P1-6) was synthesized in the same manner as in the synthesis of the polymer (P1-5) except that 3-aminopropanesulfonic acid was changed to the corresponding compound (Mn2000, a compound represented by the general formula ( (Ratio of structural unit represented by B1): 20 mol%).

(2) Preparation of lithium ion selective permeable membrane

0.12 g of the above polymer (P1-1) was dissolved in 0.8 g of dimethyl sulfoxide (DMSO), and poly (acrylonitrile-co-butadiene) (P1, Tg-20 ° C. shown in Table 1 below, manufactured by Aldrich) was prepared. After adding 2.6 g of a 11% by mass tetrahydrofuran (THF) solution, the mixture was mixed at room temperature for 30 minutes. To this mixture, 0.4 g of Li _1.5 Al _0.5 Ge _1.5 P ₃ O ₁₂ (median diameter 10 μm, manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was mixed at room temperature for 1 hour. It was adjusted. This suspension was applied on a Petri dish having a diameter of 4.9 cm, allowed to stand at room temperature overnight, and further dried by blowing air at 50 ° C. for 5 hours and vacuum-dried at 100 ° C. for 5 hours. A lithium ion selective permeable membrane 101 (thickness: 200 μm) was manufactured.

Further, the constituent materials of the lithium ion selective permeable membrane (lithium ion conductor (A), polymer

(B), the polymer (C), and the organic solvent) were subjected to Test No. Test No. 101 except that the composition of Table 1 described below was used instead of the composition of Test No. 101. Test No. 101 in the same manner as in the preparation of the lithium ion selective permeable membrane of No. 101. Lithium ion selective permeable membranes of 102 to 108 and c11 to c14 were produced. Each thickness was 200 μm. In addition, the test No. As shown in the evaluation of film forming properties described below, the lithium ion selective permeable films of c11, c12 and c14 did not have sufficient binding properties and could not be taken out as films. Test No. Although the lithium ion selective permeable membrane of c13 was formed, it had many defects, and the following lithium ion selective permeable membrane could not be evaluated.

Test No. Test Nos. 101 to 108 are the lithium ion selective permeable membranes of the present invention. c11 to c14 are lithium ion selective permeable membranes for comparison.

(3) Evaluation of lithium ion selective permeable membrane

With respect to each of the lithium ion selective permeable membranes prepared above, evaluation was made on film formability, membrane strength, lithium ion recovery rate and selectivity, and water permeability. The results are summarized in Table 1 below.

[Film formation property]

The prepared film was applied to the following evaluation criteria, and the film forming property was evaluated. Defects such as cracks in the film were observed on the film surface.

-Evaluation criteria-

A: The film had no defects such as cracks, and could be taken out of the petri dish as a film.

B: The film had one defect such as a crack, but could be taken out of the petri dish as a film.

C: The film had two or more defects such as cracks, but could be taken out of the petri dish as a film.

D: The particles were not sufficiently bound to each other and could not be taken out of the petri dish as a film.

[Film strength test: Reference test]

With respect to the produced film, a test piece having a length of 3 cm, a width of 3 cm and a thickness of 200 μm was produced. The 90 ° bending test was repeated for this test piece. After bending at an angle of 90 °, the operation of returning to the original state (angle 0 °) was counted as one, the number of times until the test piece was broken was determined, and the film strength was evaluated by applying the following evaluation criteria. In addition, the fracture of the test piece means a state in which defects such as cracks have occurred.

-Evaluation criteria-

A: 21 times or more

B: 11-20 times

C: 6 to 10 times

D: 5 times or less

[Electrodialysis test]

The produced membrane was cut into a size of 1.7 cm in diameter and 200 μm in thickness to prepare a lithium ion selective permeable membrane. In a device (manufactured by Techno Sigma) having a positive electrode 3 and a negative electrode 4 shown in FIG. 1, a prepared lithium ion selective permeable membrane 10 is arranged, and a stock solution 5 containing LiOH and NaOH at a concentration of 0.1 M each on the anode side. 10 ml of (solvent: water) was poured. Next, 10 ml of water (recovery solution 6) was poured into the cathode side, and electrodialysis was performed at a voltage of 3 V and 25 ° C. for 3 hours.

(Lithium ion recovery rate)

By measuring the lithium ion concentration of the recovery solution 6 after performing the electrodialysis for 3 hours, the ratio of lithium ions transferred from the stock solution 5 to the recovery solution 6 was determined, and the lithium ion recovery rate was evaluated by applying the following evaluation criteria. .

-Evaluation criteria-

A: 10% or more

B: 5% or more and less than 10%

C: Exceeding detection limit and less than 5%

D: below detection limit

(Lithium ion selectivity)

Ratio of lithium ions in the total amount of lithium ions and sodium ions in the recovered solution 6 after electrodialysis for 3 hours (content of Li ⁺ (mol) / [total content of Li ⁺ and Na ⁺ (mol)]) ) Was determined, and lithium ion selectivity was evaluated by applying the following evaluation criteria.

-Evaluation criteria-

A: 0.7 or more

B: 0.5 or more and less than 0.7

C: 0.3 or more and less than 0.5

D: less than 0.3

(Water permeability: Reference test)

The rate of increase in the weight of water in the recovered solution 6 before and after electrodialysis for 3 hours (([W _3h -W ₀ ] / W ₀ ) × 100%) was determined, and the water permeability was evaluated by applying the following evaluation criteria. did. W ₀ represents the weight (g) of water in the recovered solution 6 before electrodialysis for 3 hours, and W _3h represents the weight (g) of water in the recovered solution 6 after electrodialysis for 3 hours. Shown respectively.

-Evaluation criteria-

A: less than 0.3%

B: 0.3% or more and less than 0.6%

C: 0.6% or more and less than 1.0%

D: 1.0% or more

<Note for Table 1>

(1) Lithium ion conductor (A)

LAGP: Li _1.5 Al _0.5 Ge _1.5 P ₃ O ₁₂ (median diameter 10 μm, manufactured by Wako Pure Chemical Industries, Ltd.)

(2) Polymer (B)

(P1-1) to (P1-6): Polymers (P1-1) to (P1-6) synthesized above.

(CP1-1): poly (ethylene-co-acrylic acid) (manufactured by Aldrich)

(CP1-2): a polymer (cP1-1) neutralized with NaOH (neutralization ratio of 90% or more) at the time of liquid preparation.

SP value: Shows the SP value of the structural unit represented by the general formula (B1). However, for polymers (cP1-1) and (cP1-2), the SP value of the structural unit of the acrylic acid component is shown.

(3) Polymer (C)

(P1): poly (acrylonitrile-co-butadiene) (Tg-20 ° C., acrylonitrile content 37-39% by mass, manufactured by Aldrich)

(P2): polyacrylonitrile (Tg ≧ 50 ° C., manufactured by Aldrich)

(P3): Epoxidized natural rubber (Tg-15 ° C., epoxidation rate 50%, obtained from Sanyo Trading Co., Ltd.)

"-" In the table indicates that the component is not contained.

As is apparent from Table 1 above, No. c11 uses a low molecular weight organic lithium salt compound and a water-insoluble polymer (C). For c12, an anionic group-containing polymer having a carboxy group bonded directly to the polymer main chain was used. No. 14 manufactures a lithium ion selective permeable membrane using the Na salt of the anionic group-containing polymer, and in each case, the polymer (B) having a structural unit represented by the general formula (B1) in the present invention (B1) ) Is not contained. These Nos. All of c11, c12 and c14 could not be taken out from the petri dish as a film. In addition, No. In c13, a lithium ion selective permeable membrane is prepared using an anionic group-containing polymer in which a carboxy group is directly bonded to a polymer main chain and a water-insoluble polymer (C). It does not contain the polymer (B) having the represented structural unit. This No. Although c13 could be taken out from the petri dish as a film, the obtained film had many defects and could not be evaluated for performance as a lithium ion selective permeable film.

On the other hand, the lithium ion selective permeable membrane of the present invention having the polymer (B) having the structural unit represented by the general formula (B1) was excellent in film formability. Moreover, this lithium ion selective permeable membrane showed an excellent lithium ion recovery rate and lithium ion selectivity. Furthermore, the selectively permeable lithium ion membrane of the present invention was excellent in both membrane strength and water permeability.

1A, 1B Lithium ion recovery device

2 Processing tank

3 Positive electrode

4 Negative electrode

5 undiluted solution

6 Recovered liquid

10 Lithium ion selective permeable membrane

11 Stock solution storage tank

12 Recovery liquid storage tank

13a-e piping

14a-e pump

15 Lithium-containing compound recovery department

16 Power supply

17 stirrer

18 Turntable

100 Lithium-containing compound recovery device

Claims

A selectively permeable lithium ion membrane comprising a lithium ion conductor (A) and a polymer (B) having a structural unit represented by the following general formula (B1).

In the above formula, L 1 and L 2 each independently represent an alkylene group which may have a substituent, R 1 to R 3 each independently represent a hydrogen atom or an alkyl group, and A represents —NR 4 − , —O— or —S—, R 4 represents a hydrogen atom or an alkyl group, and Y B1 represents an anionic group having a lithium ion as a counter ion. * Indicates a binding site as a structural unit of the polymer.
The lithium ion selective permeable membrane according to claim 1, wherein the SP value of the structural unit represented by the general formula (B1) is 14 or more and 24 or less.
The lithium ion selective permeable membrane according to claim 1 or 2, wherein the structural unit represented by the general formula (B1) is a structural unit represented by the following general formula (B2).

In the above formula, L 21 and L 22 each independently represent an alkylene group having 1 to 7 carbon atoms, R 21 to R 23 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Y B2 represents It has the same meaning as YB1. * Indicates a binding site as a structural unit of the polymer.
The anionic group is -SO 3 - Li is +, the lithium ion permselective membrane according to any one of claims 1 to 3.
A water-insoluble polymer (C) different from the polymer (B), wherein at least one of a cyano group, an amide group, an amino group, a hydroxy group, a sulfanyl group, an ether bond, a sulfide bond, and a urethane bond is provided. The lithium ion selective permeable membrane according to any one of claims 1 to 4, wherein the membrane comprises a water-insoluble polymer (C) having a glass transition temperature of 0 ° C or lower.
A lithium ion recovery device comprising the lithium ion selective permeable membrane according to any one of claims 1 to 5.
A lithium-containing compound recovery device comprising the lithium ion recovery device according to claim 6.
A method for recovering lithium ions, comprising recovering lithium ions using the lithium ion selective permeable membrane according to any one of claims 1 to 5.