1. An electrolysis apparatus for recovering lithium ions from a raw material, comprising:

a pair of electrodes; and a process for the preparation of a coating,

a cation exchange membrane provided between the pair of electrodes and having lithium ion conductivity;

the cation exchange membrane allows the lithium ions to pass through more cations than other cations among the cations contained in the raw material.

2. The electrolysis apparatus according to claim 1, further comprising a voltage applier that applies a voltage between the pair of electrodes.

3. The electrolytic device according to claim 1, wherein the raw material is an organic solution or a saturated aqueous solution, and the cation exchange membrane is a titanium aluminum lithium phosphate-based ceramic having a crystal structure of a sodium super-ionic conductor type.

4. The electrolytic device according to claim 1, wherein the raw material is an aqueous solution, and the cation exchange membrane is a titanium aluminum lithium phosphate-based ceramic having a crystal structure of a sodium super ionic conductor type, the surface of which is covered with a coating material.

5. The electrolysis apparatus according to claim 4, wherein the coating material is a lithium phosphate oxynitride glass.

Background

Conventionally, there is known a technique of recovering lithium from seawater or an electrolyte of an old battery by adsorbing and desorbing lithium ions by an adsorbent such as manganese oxide (see, for example, patent document 1).

[ Prior Art document ]

(patent document)

Patent document 1: japanese Kohyo publication No. 2012-504190

Disclosure of Invention

[ problems to be solved by the invention ]

However, in the above-mentioned technique, since the adsorbent acts not only on lithium but also on metals such as calcium and sodium, it is difficult to selectively recover lithium.

The present invention has been made in view of the above problems, and has an object to provide an electrolysis device that can extract lithium from the grass of the grain .

[ means for solving problems ]

(1) The electrolytic device (for example, the electrolytic device 1) according to the present invention recovers lithium ions (for example, the lithium ions Li) from a raw material (for example, the raw material M)⁺) The electrolytic device of (1), comprising: a pair of electrodes (for example, the following pair of electrodes 3, 4); and a cation exchange membrane (for example, the following cation exchange membrane 5) which is provided between the pair of electrodes and has lithium ion conductivity; the cation exchange membrane is formed by making the lithium ion in the cation contained in the raw material more abundant than other cations (for example, calcium ion Ca described below)²⁺Sodium ion Na⁺) More.

According to the invention (1), lithium (lithium hydroxide) can be selectively recovered by using a cation exchange membrane capable of allowing lithium ions contained in the raw material to pass through more cation than other cations. Therefore, according to the invention (1), lithium (lithium hydroxide) can be recovered from, for example, seawater at a high yield.

(2) The electrolysis device according to (1) may further include a voltage applier that applies a voltage between the pair of electrodes.

According to the invention of (2), by providing the voltage application device capable of applying a voltage between the pair of electrodes, the oxidation reaction and the reduction reaction of both electrodes can be promoted, and as a result, the rate of recovering lithium is increased.

(3) The electrolytic device according to (1) or (2) may be one in which the raw material is an organic solution or a saturated aqueous solution, and the cation exchange membrane is a titanium aluminum lithium phosphate (LTAP) ceramic having a crystal structure of a sodium super ion conductor (NASICON) type.

According to the invention of (3), by using the LTAP-based ceramic having the NASICON-type crystal structure as a cation exchange membrane capable of passing lithium ions contained in the raw material more than other cations and using an organic solution or a saturated aqueous solution as the raw material, it is possible to selectively recover lithium (lithium hydroxide) while suppressing deterioration of the cation exchange membrane.

(4) The electrolytic device according to (1) or (2) may be one in which the raw material is an aqueous solution and the cation exchange membrane is an LTAP-based ceramic having a NASICON type crystal structure and a surface of which is covered with a coating material.

According to the invention of (4), according to the use of the LTAP-based ceramic having the NASICON-type crystal structure with the surface covered with the coating material as the cation exchange membrane capable of passing more lithium ions contained in the raw material than other cations, the deterioration of the cation exchange membrane can be suppressed despite the raw material being an aqueous solution, and lithium (lithium hydroxide) can be selectively recovered.

(5) The electrolytic device according to (4), wherein the coating material is a lithium phosphate oxynitride glass.

According to the invention of (5), the surface of the cation exchange membrane made of the LTAP-based ceramic having the NASICON type crystal structure is covered with the lithium phosphate oxynitride glass, and the deterioration of the cation exchange membrane due to the aqueous solution can be more reliably suppressed.

(Effect of the invention)

According to the present invention, an electrolytic device capable of selectively recovering lithium can be obtained.

Drawings

FIG. 1 is a schematic view of an electrolytic apparatus according to an embodiment of the present invention.

Detailed Description

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings.

[ embodiment 1 ]

First, the structure of the electrolysis apparatus 1 according to embodiment 1 will be described with reference to fig. 1. FIG. 1 is a schematic view of an electrolyzer 1.

As shown in fig. 1, the electrolysis apparatus 1 includes: a center flow path 2, a pair of electrodes 3,4, a cation exchange membrane 5, a raw material side inflow path 6, a drain path 7, a raw material side exhaust path 8, a water side inflow path 9, a lithium recovery path 10, a recovery side exhaust path 11, a raw material side pump 12, a water side pump 13, and a power source device 14.

The central channel 2 is a channel having a pair of electrodes 3 and 4 provided on both sides. This central flow path 2 is the following flow path: the cation exchange membrane 5 provided between the pair of electrodes 3,4 is divided into 2 regions 2a,2b, and lithium ions Li are made to pass through the cation exchange membrane 5⁺From the basin 2a to the basin 2 b. The flow field 2a communicates between the raw material side inflow path 6 and the drain path 7, and allows the raw material M flowing in from the raw material side inflow path 6 to flow out to the drain path 7. The flow field 2b is connected between the water-side inflow path 9 and the lithium recovery path 10, and the low-concentration lithium hydroxide aqueous solution W having flowed in from the water-side inflow path 9 is converted (more than 99%) into a high-purity high-concentration lithium hydroxide aqueous solution L, which is then caused to flow out to the lithium recovery path 10. As the raw material M, for example, an organic solution or a saturated aqueous solution (for example, saturated seawater) of a lithium ion battery that has been used can be used. The raw material M contains lithium ion Li⁺And, for example, Ca ion²⁺Sodium ion Na⁺Chloride ion Cl^-And the like.

The pair of electrodes 3,4 are disposed on both sides of the central passage 2, and electrons e are generated by applying a direct current from a power supply device 14^-From the anode dimensionally stable electrode 3 to the cathode dimensionally stable electrode 4. For example, titanium mesh coated with iridium can be used for the electrode 3. For example, nickel mesh can be used for the electrode 4. To be 25mA/cm²In the method (1), a current is applied to the pair of electrodes 3,4, and the voltage at this time is an arbitrary value.

The cation exchange membrane 5 is provided between the pair of electrodes 3,4, and divides the central channel 2 into 2 flow fields 2a,2 b. The cation exchange membrane 5 has lithium ion conductivity and has a function of making only the originalLithium ion Li in the cations contained in Material M⁺By the property of not allowing other cations (e.g. calcium ion Ca)²⁺Sodium ion Na⁺) And (4) passing. Or, specifically, the cation-exchange membrane 5 is capable of chemically reacting (2 Cl) the raw material M flowing through the flow field 2a^-→Cl₂+2e^-) And a chemical reaction (2H) is caused in the low-concentration aqueous lithium hydroxide solution W flowing through the flow field 2b⁺+2e^-→H₂，2OH^-+2Li⁺→ 2LiOH), lithium ion Li⁺From the basin 2a to the basin 2 b. Although this chemical reaction occurs without applying an electric pressure between the pair of electrodes 3,4, the chemical reaction can be promoted by applying an electric pressure between the pair of electrodes 3, 4.

Specifically, as the cation-exchange membrane 5 having a characteristic of passing only lithium ions without passing other cations contained in the raw material M, it is possible to preferably use a NASICON (sodium super ionic conductor) type crystal structure having rhombohedral crystals and made of Li_1+x+yAl_xTi_2-xSi_yP_3-yO₁₂And (x is 0.3 and y is 0.2) LTAP-based ceramics. The lithium scavenging property of the cation exchange membrane 5 is preferably 99% or more.

The raw material side inflow path 6 connects the flow field 2a of the central flow path 2 and allows the raw material M to flow into the flow field 2 a.

The liquid discharge path 7 connects the flow field 2a in the central flow path 2, and allows the raw material M treated by the flow field 2a to flow therein.

The raw material side exhaust path 8 is an exhaust path branched from the liquid discharge path 7, and is a path for discharging a gas (for example, chlorine gas Cl) generated from the raw material M treated by the flow field 2a₂) And (4) discharging.

The water-side inflow path 9 connects the flow field 2b of the central channel 2 and allows the low-concentration lithium hydroxide aqueous solution W to flow into the flow field 2 b.

The lithium recovery path 10 connects the flow field 2b in the central flow field 2, and allows a high-purity, high-concentration lithium hydroxide aqueous solution L, which has been treated with the flow field 2b and is generated from a low-concentration lithium hydroxide aqueous solution W, to flow therein.

The recovery-side exhaust path 11 is an exhaust path branched from the lithium recovery path 10, and is a path for generating a gas (for example, hydrogen gas H) from the low-concentration lithium hydroxide aqueous solution W treated in the flow field 2b₂) And (4) discharging.

The raw material side pump 12 is provided in the raw material side inflow path 6, and sends the raw material M in the raw material side inflow path 6 to the flow field 2a in the central flow path 2.

The water-side pump 13 is provided in the water-side inflow path 9, and sends the low-concentration lithium hydroxide aqueous solution W in the water-side inflow path 9 to the flow field 2b in the central flow path 2.

The power supply device 14 is electrically connected to the pair of electrodes 3,4, and applies a dc current to the pair of electrodes 3,4 as necessary.

Next, the operation of the electrolytic apparatus 1 was performed in accordance with the procedure of FIG. 1.

As shown in fig. 1, by driving the raw material side pump 12 and the water side pump 13, the raw material M is caused to flow from the raw material side inflow path 6 into the flow field 2a in the central flow path 2, and the low-concentration lithium hydroxide aqueous solution W is caused to flow from the water side inflow path 9 into the flow field 2b in the central flow path 2.

The raw material M flowing through the flow field 2a is chemically reacted (2 Cl) by the cation exchange membrane 5^-→Cl₂+2e^-) And the aqueous solution W flowing through the flow path 2b is chemically reacted (2H)⁺+2e^-→H₂，2OH^-+2Li⁺→ 2LiOH), lithium ion Li⁺From the basin 2a to the basin 2 b.

The treated raw material M flows into the liquid discharge path 7 from the flow field 2a in the central flow path 2, and the gas (chlorine Cl) generated from the raw material M₂) And discharged from the raw material side exhaust passage 8. Further, a high-purity high-concentration lithium hydroxide aqueous solution L generated from a low-concentration lithium hydroxide aqueous solution W by a chemical reaction flows from the flow path 2b in the central flow path 2 into the lithium recovery path 10, and a gas (hydrogen gas H) generated from the low-concentration lithium hydroxide aqueous solution W is generated₂) And is discharged from the recovery-side exhaust path 11.

According to the electrolysis apparatus 1 of the present embodiment, the following effects can be exhibited.

First, in the electrolytic device 1 according to the present embodiment, the cation exchange membrane 5 having lithium ion conductivity is set to have a characteristic of allowing lithium ions in the cations contained in the raw material M to pass through more than other cations. Thus, lithium (lithium hydroxide) can be selectively recovered. Therefore, according to the present embodiment, lithium (lithium hydroxide) can be recovered from, for example, seawater in a high yield.

In addition, the present embodiment is configured as follows: a power supply device 14 capable of applying a DC current between the pair of electrodes 3,4 is provided. This promotes both oxidation and reduction reactions, and as a result, the rate of lithium recovery can be increased.

In addition, the present embodiment is configured as follows: an organic solution or a saturated aqueous solution is used as the raw material M, and an LTAP-based ceramic having a NASICON-type crystal structure is used as the cation exchange membrane 5. Accordingly, lithium (lithium hydroxide) can be selectively recovered while suppressing deterioration of the cation exchange membrane 5.

[ 2 nd embodiment ]

Next, the structure of the electrolysis apparatus 1 according to embodiment 2 will be described. Here, only the differences from embodiment 1 will be described. The electrolysis apparatus 1 according to embodiment 2 of differs from embodiment 1 in the following.

Specifically, the cation exchange membrane of the present embodiment is an LTAP-based ceramic having a NASICON-type crystal structure with its surface covered with a coating material. That is, the cation exchange membrane according to embodiment 1 is a cation exchange membrane in which the surface of the cation exchange membrane is covered with a coating material.

The coating material is formed by the following method: the adsorption is performed by vapor deposition. Examples of such coating materials that can be used are: a lithium oxynitride phosphate glass; or lithium titanate, lanthanum lithium zirconate, and the like. The film thickness of the coating material is preferably 10nm or more and 1000nm or less, and more preferably 100nm from the viewpoint of the resistance of the electrolyzer and the durability of the cation exchange membrane. For example, an aqueous solution (e.g., seawater) can be used as the raw material M.

According to the electrolysis apparatus 1 of the present embodiment, the following effects can be exhibited.

The present embodiment is configured as follows: an aqueous solution is used as a raw material, and an LTAP-based ceramic having a NASICON type crystal structure with its surface covered with a coating material is used as a cation exchange membrane. Accordingly, although the raw material is an aqueous solution, lithium (lithium hydroxide) can be selectively recovered while suppressing deterioration of the cation exchange membrane.

In addition, the present embodiment is configured as follows: lithium phosphate oxynitride glass was used as the coating material. Accordingly, by covering the surface of the cation exchange membrane made of the LTAP-based ceramic having the NASICON type crystal structure with the lithium phosphate oxynitride glass, the deterioration of the cation exchange membrane due to the aqueous solution can be more reliably suppressed.

The present invention is not limited to the above embodiments, and variations, improvements, and the like are included in the present invention within a range in which the object of the present invention can be achieved. For example, the electrolysis apparatus may further include a heating device capable of heating the raw material and the apparatus. Accordingly, the oxidation reaction and the reduction reaction of both electrodes can be promoted by heating the raw material and the apparatus, and as a result, the speed of recovering lithium is increased. In the above embodiment, only Li ions are used⁺The cation exchange membrane passed through is used as the cation exchange membrane 5, but the cation exchange membrane 5 may also be a cation exchange membrane having the following characteristics: the lithium ion conductive material M is made to contain lithium ions Li in the cations⁺More than other cations (e.g. calcium ion Ca)²⁺Sodium ion Na⁺) More.

Reference numerals

1: electrolysis device

2: center flow path

2a,2 b: drainage basin

3. 4: electrode for electrochemical cell

5: cation exchange membrane

6: raw material side inflow path

7: liquid discharge path

8: raw material side exhaust path

9: water side inflow path

10: lithium recovery path

11: recovery side exhaust path

12: raw material side pump

13: water side pump

14: power supply device

M: raw materials

W: low-concentration lithium hydroxide aqueous solution

L: high-concentration lithium hydroxide aqueous solution

Li⁺: lithium ion

Ca²⁺: calcium ion (other cations)

Na⁺: sodium ion (other cations)

Cl^-: chloride ion

e^-: electronic device