KR102186074B1 - Concentration method of lithium by electrodialysis - Google Patents

Abstract

The present invention provides a method for concentrating lithium by electrodialysis, comprising a process of separating lithium ions by electrodialysis of a solution containing lithium ions, in an electrodialysis apparatus including an electrode chamber, a dilution chamber, and a concentration chamber, formed by alternating at least one pair of cation exchange membranes and anion exchange membranes between a positive electrode and a negative electrode, wherein the method comprises: a first step of introducing a lithium ion-containing solution at a concentration of 1.0 g/L or more in a volume ratio of 1 : 1 to 10 : 1, as a raw material solution, into the dilution chamber and the concentration chamber and introducing 0.1 to 1.0 M Na_2SO_4 solution as an electrode solution to the electrode chamber; a second step of performing electrodialysis by applying a DC voltage of 8 to 12 V as an electrode voltage between the positive electrode and the negative electrode; and optionally a third step of introducing a concentrate collected in the concentration chamber in the step 2 into the raw material solution in the step 1.

Description

Concentration method of lithium by electrodialysis {CONCENTRATION METHOD OF LITHIUM BY ELECTRODIALYSIS}

The present invention relates to a method for concentrating lithium, and more particularly, to a method for concentrating lithium by electrodialysis from a lithium-containing battery waste liquid.

Lithium is a resource used as a key component for secondary batteries or energy storage devices such as electric vehicles, smartphones, and notebooks. Research on lithium-ion batteries is actively being conducted. As the electric vehicle market grows, the demand for lithium-ion batteries increases. However, due to a lack of supply, prices have surged more than three times since 2015.

Since Korea has little lithium reserves, it is a situation that relies on imports for lithium resources necessary for the industry, and a shortage of supply versus demand in the world can cause a major blow to the domestic industry. Therefore, there is an urgent need for a way to stably supply and supply lithium in Korea.

Metallic lithium is about twice as much in brine than in ore. Therefore, research on the recovery of lithium from brine is actively being conducted, but there are many impurities such as Mg ²⁺ and Ca ^{2+ in} brine, requiring a purification process, and due to the low lithium concentration, a large amount of brine must be concentrated by evaporation. Therefore, there is a problem that the energy consumption is high and the process time is long.

A number of methods have also been proposed for separating and concentrating lithium from seawater, brine, or lithium-containing battery waste using electrodialysis. The electrodialysis method is advantageous in terms of energy consumption and processing time as it can separate only desired ions without evaporating the solution, but when the lithium ion content is low or the operating voltage is high, a limiting current density phenomenon occurs, and thereby ion separation membrane There is a problem that it is contaminated. Therefore, it is limited to apply the electrodialysis method to seawater or brine with a low lithium ion concentration.

Patent Document 1 discloses a method of economically extracting high-purity lithium phosphate from brine, including the step of separating lithium contained in brine by electrodialysis by an electrodialysis device equipped with a monovalent cation exchange membrane, but electrodialysis The volume ratio and voltage are not described at all as the process conditions of.

Patent Document 2 proposes to apply electrodialysis to a process of recovering lithium contained in waste liquid discharged from a waste lithium battery recycling process. However, the process is redundant and complicated, such as applying electrodialysis to a solution in which sulfate ions, magnesium ions, and calcium ions have been removed first, and there is no description or configuration of electrodialysis.

Waste lithium batteries are not waste, but important resources, but it is difficult to find commercial examples of recycling lithium from lithium-containing battery waste liquid, which has an impact on the lack of recycling technology that efficiently separates and concentrates lithium from lithium battery waste liquid or lithium-containing battery waste liquid. It can be seen that there is.

Therefore, in order to develop a technology for recycling waste lithium batteries, a method of efficiently separating and concentrating lithium from lithium battery waste liquid or lithium-containing battery waste liquid by electrodialysis has been studied.

Republic of Korea Patent Publication No. 10-2012-0089515 (published on August 13, 2012) Korean Registered Patent Publication No. 10-1713600 (announced on Mar. 2, 2017)

An object of the present invention is to provide a method for performing electrodialysis economically and efficiently by minimizing water movement without generating a limiting current density in a method of separating and concentrating lithium from lithium-containing battery waste liquid by electrodialysis. Is to do.

In order to solve the above object, the present invention provides a method of concentrating lithium by separating lithium by electrodialysis of a solution containing lithium ions in an electrodialysis apparatus. The electrodialysis apparatus includes at least one pair of cation exchange membranes between an anode and a cathode. And an electrode chamber, a dilution chamber, and a concentration chamber formed by alternating anion exchange membranes, and the method includes the following steps.

(Step 1) Into the dilution chamber and the concentration chamber, a solution containing lithium ions having a concentration of 1.0 g/L or more as a raw material solution is added in a volume ratio of 1:1 to 10:1, and 0.1 to 1.0M Na ₂ as an electrode solution in the electrode chamber Introducing a SO ₄ solution; And

(Step 2) Electrodialysis by applying a DC voltage of 8V to 12V as an electrode voltage between the anode and the cathode.

According to an embodiment of the present invention, the cation exchange membrane and the anion exchange membrane are alternately arranged at least 5 pairs.

According to an embodiment of the present invention, the raw material solution may be added to the dilution chamber and the concentration chamber in a volume ratio of 2:1 to 7:1.

According to an embodiment of the present invention, the raw material solution is divided into a predetermined total volume by a volume ratio selected from 1:1 to 10:1, preferably 2:1 to 7:1, in a dilution chamber and a concentration chamber. Is put in.

According to an embodiment of the present invention, a 0.2 to 0.8M Na ₂ SO ₄ solution may be added as an electrode solution to the electrode chamber.

According to an embodiment of the present invention, the cation exchange membrane may be selected from a monovalent cation exchange membrane.

According to an embodiment of the present invention, the electrodialysis may be performed until the electrical conductivity of the dilution chamber becomes 1.0 mS/cm or less.

According to an embodiment of the present invention, the solution containing lithium ions may contain lithium at a concentration of 2.0 g/L or more.

According to an embodiment of the present invention, the solution containing lithium ions may be a waste lithium battery.

According to an embodiment of the present invention, (Step 3) the step of introducing the concentrate recovered in the concentration chamber in Step 2 as the raw material solution in Step 1; may further include.

According to an embodiment of the present invention, the process including Step 1, Step 2, and Step 3 may be repeated 2 to 5 times.

The method of separating and concentrating lithium from the lithium-containing battery waste liquid according to the present invention by electrodialysis does not generate limiting current density and minimizes water movement, thereby effectively improving electrodialysis time, water recovery rate, and average flow rate. In addition, lithium can be concentrated to a higher concentration by multi-stage electrodialysis.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a conceptual diagram showing a principle in which ions are concentrated or diluted through ion movement in the electrodialysis apparatus used in the present invention.
2 is a schematic diagram showing a schematic configuration of an electrodialysis device used in the present invention and a cell configuration in a cartridge.
3A is a diagram showing the lithium concentration in the resulting concentrate when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 4/1 at electrode voltages 8V and 10V.
3B is a diagram showing the lithium concentration in the resulting concentrate when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at an electrode voltage of 10V.
Figure 4 shows the change in electrical conductivity in the concentration chamber (C) and the dilution chamber (D) when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at the electrode voltage of 10 V. It is a drawing.
5 is a diagram showing energy consumption when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at an electrode voltage of 10 V.
6 is a diagram showing an average flow rate when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at an electrode voltage of 10 V.

Before describing the present invention in detail, terms or words used in the present specification should not be unconditionally limited and interpreted in a conventional or dictionary meaning, and in order for the inventors of the present invention to describe their invention in the best way It should be noted that the concepts of various terms can be appropriately defined and used, and furthermore, these terms or words should be interpreted as meanings and concepts consistent with the technical idea of the present invention.

That is, the terms used in this specification are only used to describe a preferred embodiment of the present invention, and are not intended to specifically limit the content of the present invention, and these terms are used to describe various possibilities of the present invention. It should be noted that this is a term defined in consideration.

In addition, in this specification, it should be understood that the singular expression may include a plural expression unless clearly indicated in a different meaning in the context, and even if similarly expressed in the plural, the singular expression may include the meaning of the singular number. do.

Throughout the present specification, when a component is described as "including" another component, it does not exclude any other component, but further includes any other component unless otherwise indicated. It could mean you can do it.

Further, in the following description of the present invention, a detailed description of a configuration that is determined to unnecessarily obscure the subject matter of the present invention, for example, a known technology including the prior art may be omitted.

The present invention will be described in more detail below.

1. Raw material solution

In the present invention, the raw material solution may be selected from a solution containing lithium at a concentration of 1.0 g/L or more, preferably 2.0 g/L or more.

In the present invention, the raw material solution may contain other metal cations such as Na ⁺ , Ca ²⁺ , and Mg ^{2+ in} addition to lithium ions. Other metal cations are preferably present in an amount similar to or less than that contained in seawater or brine from the viewpoint of process speed, limiting current density, and water migration. When the concentration of metal cations including lithium increases, the likelihood of occurrence at a lower voltage limiting current density increases.

In the present invention, the raw material solution contains monovalent anions such as Cl ^- and Br ^- and divalent anions such as CO ₃ ^2- and SO ₄ ^2- . The type and concentration of anions are not particularly limited, but a type that can be easily moved through the anion exchange membrane is preferable from the viewpoint of process speed, energy consumption, and pot life of the membrane.

The lithium battery waste liquid remaining after extracting the valuable metals from the waste lithium battery contains less divalent cations such as Ca ²⁺ and Mg ²⁺ and more lithium ions, specifically about 3 when compared to seawater or brine. Since it contains more than g/L, it can be advantageously applied to the method of concentrating lithium by the electrodialysis method according to the present invention.

Therefore, according to an embodiment of the present invention, the raw material solution may be selected from a solution containing lithium at a concentration of 1.0 g/L or more, preferably 2.0 g/L or more, and more preferably 3.0 g/L or more. .

According to an embodiment of the present invention, the raw material solution may be a lithium battery waste solution or a lithium-containing battery waste solution.

2. Electrodialysis device

Electrodialysis is a process mainly used for concentration of target components and separation of impurities by selectively passing ions through an ion exchange membrane in an electric field.The electrodialysis device includes an anode, a cathode, and one or more ion exchange membranes between them. Preferably, it may be prepared by alternately installing a cation exchange membrane and an anion exchange membrane.

The electrodialysis apparatus usable in the present invention and its basic principle are shown in FIG. 1. As shown in Figure 1, the anode (+) electrode and the cathode (-) electrode are located at both ends, between them, a cation exchange membrane (indicated by C) and an anion exchange membrane (indicated by A) one or more pairs are alternately arranged In addition, between each of the exchange membranes, although not shown in FIG. 1, there is a spacer of a non-insulating material that separates the exchange membrane from each other although ions and electrolytes are movable.

The liquid chamber is divided by the cation exchange membrane and the anion exchange membrane, and the liquid chamber in which the concentration increases as the desired ions flow in through the exchange membrane is referred to as the concentration chamber, and the liquid chamber in which the concentration decreases as the desired ions flow through the exchange membrane is referred to as the dilution chamber.

As the cation exchange membrane and the anion exchange membrane are alternately arranged, the concentration chamber and the dilution chamber also appear alternately. When the raw material solution is put into the concentration chamber and the dilution chamber and a voltage is applied between the anode and the cathode, charge transfer occurs, and ions in the material solution move toward the cathode and the anode to be concentrated or diluted. The liquid chamber including the anode and the cathode is referred to as an anode electrode chamber and a cathode electrode chamber, respectively, and an aqueous solution of an electrolyte such as NaCl, HCl, and Na ₂ SO ₄ is injected into the electrode chamber as an electrode solution.

The rectifier used in the electrodialysis device can be finely adjusted in units of 0.1 V and 0.1 A within the range of voltage 0 to 15 V and current 0 to 50 A, and can be used without limitation if constant voltage and constant current supply is possible. For example, DH-R50ST (JISANG ELECTRIC Co., LTD) can be mentioned.

According to an embodiment of the present invention, in the electrodialysis apparatus, 5 or more pairs of cation exchange membranes and anion exchange membranes may be alternately arranged, preferably at least 10 pairs, and they may be used in a form included in a cartridge.

In the present invention, in the electrodialysis apparatus, a cation exchange membrane and an anion exchange membrane are alternately installed, and then one cation exchange membrane is further installed outside the outermost anion exchange membrane, or one anion exchange membrane is installed outside the outermost cation exchange membrane. You can install more. 1 is a conceptual diagram showing the principle of concentration or dilution of ions through ion movement in an electrodialysis apparatus including a plurality of ion exchange membranes. After alternately installing three pairs of cation exchange membranes and anion exchange membranes, the outermost anion exchange membrane It shows a structure in which one more cation exchange membrane is installed on the outside.

3. Ion Exchange Membrane

In the present invention, the ion exchange membrane means having ion selectivity that can selectively separate anions or cations in an aqueous solution, and is generally manufactured in the form of a membrane made of a polymer matrix, and fixed ions fixed inside the membrane ( fixed ion) as a cation exchanger or anion exchanger.

Ion exchange membranes are classified into homogeneous membranes and heterogeneous membranes according to their structure, and are classified into desalination membranes, concentration membranes, and specially selected permeable membranes, etc., depending on their use. It can be classified as such.

In the present invention, the ion exchange membrane is not particularly limited, and an ion exchange membrane commonly used in the field of electrodialysis or an electrodialysis apparatus may be used.

Specifically, -SO in the film inside and / or surface of a cation exchange membrane ^{_{3 -, -COO -, -PO 4}} 2-, -HPO 2 -, an anion group, preferably such as -AsO ₃ ^2- or ^3- -SeO Advantageously a sulfonic acid group (-SO ₃ ^-) is the anion exchange membrane is a film inside and / or surface can be used, that is fixed ^{_{-NH 3 +, -RNH 2 +,}} -R 2 NH +, -R 3 N ^A cationic group such as ⁺ , -R ₃ P ⁺ or -R ₂ S ⁺ , preferably a quaternary ammonium base (-R ₃ N ⁺ ) fixed thereto may be used.

In one embodiment of the present invention, the cation exchange membrane is there is one that can pass through a monovalent lithium ion be selected from cation exchange membranes, for example, -SO ₃ ^-, -COO ^- or -HPO ₂ ^- anions, such as the group , preferably a sulfonic acid group (-SO ₃ ^-), it may be mentioned a fixed ion exchange membranes.

4. Electrode solution

In the present invention, the electrode liquid injected into the anode electrode chamber (or anode chamber) and the cathode electrode chamber (or cathode chamber) may be the same or different. The electrolyte used in the electrode solution is not particularly limited, and an electrolyte commonly used in the field of electrodialysis or electrodialysis apparatus may be used, for example, HCl, NaCl and Na ₂ SO ₄ , preferably HCl and Na ₂ SO ₄ , more preferably Na ₂ SO ₄ may be mentioned.

The concentration of the electrode solution is not particularly limited, but may be generally selected from 0.1 to 2M, preferably 0.2 to 1.5M, more preferably 0.3 to 1.0M.

According to an embodiment of the present invention, a Na ₂ SO ₄ solution as an electrode solution may be used in a concentration selected from 0.1 to 1.0 M, preferably 0.2 to 0.8 M, more preferably 0.3 to 0.7 M.

5. Water movement and volume ratio

In the electrodialysis process, the water movement phenomenon that reduces the concentration rate by moving water from the dilution chamber to the concentration chamber occurs due to an osmotic pressure phenomenon or an electro-osmosis phenomenon due to a difference in concentration. In the present invention, mainly hydrated ions When moving under this potential gradient, water movement occurs due to electrolytic osmosis, which also moves water.

This water movement phenomenon is one of the important variables to be considered when implementing the actual electrodialysis process industrially. It can be prevented because it disturbs the electrodialysis process by changing the volume and electrical conductivity of the solution in the dilution chamber and concentration chamber. There is a need for a plan.

In the present invention, the raw material solution may be added to the dilution chamber and the concentration chamber in a volume ratio of 1:1 to 10:1.

According to an embodiment of the present invention, the raw material solution may be added to the dilution chamber and the concentration chamber in a volume ratio of 2:1 to 7:1, respectively.

According to an embodiment of the present invention, the raw material solution is divided into a volume ratio of 1:1 to 10:1, preferably 2:1 to 7:1 in a predetermined total volume, and added to the dilution chamber and the concentration chamber, respectively. Can be.

In the present invention, injecting the raw material solution into the dilution chamber and the concentration chamber at a specific volume ratio, for example, 4:1, without setting the total volume Volume 500mL), 800mL:200mL (total volume 1000mL), 1200mL:300mL (total volume 1500mL), or 1600mL:300mL (total volume 1900mL).

In the present invention, injecting the raw material solution into the dilution chamber and the concentration chamber from a predetermined total volume to a specific volume ratio, for example, in a volume ratio of 4:1 from 1000 mL of the total volume, dividing the raw material solution into an amount of 800 mL and 200 mL. It means that it is put into the chamber and the concentration chamber respectively. In addition, when the raw material solution is added in a volume ratio of 9:1 in a total volume of 1000 mL, it means that the raw material solution is divided into 900 mL and 100 mL and added to the dilution chamber and the concentration chamber respectively.

In the present invention, when the total volume of the raw material solution introduced into the dilution chamber and the concentration chamber is set constant, when the applied voltage is around 10 V, the volume ratio (V _D /V _C ) is 2:1 to 6:1, preferably Preferably, it may be selected from 3:1 to 5:1, most preferably around 4:1, and in this case, lithium can be concentrated to a high concentration.

On the other hand, when electrodialysis is performed by setting the total volume constant, the osmotic pressure phenomenon may worsen as the volume ratio (V _D / V _C ) increases, so that the concentration rate of lithium may increase and then decrease, so 10:1 These volume ratios may not be desirable. The experimental results show that when the volume ratio (V _D /V _C ) is around 3:1, the concentration ratio and average flow rate of lithium are high, and the energy consumption is low.

6. Limit current density and voltage

In the electrodialysis process, ions in a solution move under a potential gradient as an electric field is applied, and ion transfer in the electrodialysis cell occurs in three processes.

First, ions are moved by mixing force and potential gradient in the turbulent formation region by spacers, and ions are moved only by electromotive force in the ion exchange membrane.

On the other hand, a desalted laminar boundary layer is formed between the membrane and the turbulent flow region. When the current density is increased, ions in the boundary layer rapidly decrease, resulting in concentration polarization. If this concentration polarization becomes severe, the electrical resistance increases, the required power rapidly increases, and the phenomenon of water decomposition may cause pH changes.This causes various problems during the operation of the electrodialysis process, so the current density that causes the concentration polarization, i.e., the limiting current It must be manipulated so as not to exceed the Limiting Current Density.

Therefore, when it is desired to separate and concentrate the ions contained in the electrolyte by electrodialysis, it is important to appropriately determine the voltage between the anode and the cathode (ie, electrode voltage) so as not to exceed the limit current density.

In the present invention, the electrode voltage applied between the anode and the cathode may be selected from 5 to 15V, preferably 7 to 13V, more preferably 8 to 12V as a DC voltage. When the electrode voltage exceeds 15V, in some cases, when the concentration of metal cations exceeds 12V in a solution with a high concentration of metal cations, there may be a problem that limiting current density occurs. Therefore, when considering the limit current density, electrodialysis time (ie, process time), water recovery rate, and average flow rate, the electrode voltage is preferably 9 to 11V, and most preferably around 10V.

7. Multi-stage electrodialysis

In the present invention, after the end of step 2, electrodialysis can be performed in multiple stages by re-injecting the concentrated solution recovered in the concentration chamber into the raw material solution of step 1, whereby the concentration of concentrated lithium can be further increased. have.

Accordingly, in an embodiment of the present invention, (Step 3) the step of introducing the concentrate recovered in the concentration chamber in Step 2 into the raw material solution in Step 1 may be additionally performed.

In one embodiment of the present invention, by repeating a series of processes including Step 1, Step 2 and Step 3 several times, specifically, 2 times, 3 times, 4 times, 5 times or more, preferably By repeating 2 to 5 times, lithium can be concentrated to a higher concentration.

In another embodiment of the present invention, a series of processes including steps 1, 2, and 3 are repeated several times by using an electrodialysis device to which a pair of ion exchange membranes are applied, specifically 5 times. Alternatively, it may be repeated 10 or more times.

In the present invention, the electrodialysis process is an environmentally friendly process that generates little by-products and does not require additional chemical treatment for reuse, and provides an advantageous effect in terms of energy efficiency because additional energy conversion other than electrical energy is not required. .

In the present invention, by controlling the volume ratio of the initial solution supplied to the dilution chamber and the concentration chamber within the scope of the present invention, it is possible to effectively reduce or prevent disturbance of the electrodialysis process due to the water movement phenomenon, from the viewpoint of process management. Also provides a beneficial effect

In the present invention, by controlling the electrode voltage between the positive electrode and the negative electrode within the range of the present invention, it is possible to efficiently control the electrodialysis time, water recovery rate, average flow rate, etc. without generating a limiting current density.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are for explaining the present invention more specifically, and the scope of the present invention is not limited by the following examples. The following examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

Example

(1) lithium-containing raw material solution

The raw material solution used in the examples of the present invention has the composition shown in Table 1 below. In the table, P means the total phosphorus content.

Li ⁺ Na ⁺ SO ₄ ^2- P Mg ²⁺ Ca ²⁺ Concentration (g/L) 3.3 60 179 4 ppm 4 ppm 2 ppm

(2) Electrodialysis device and ion exchange membrane

In the embodiment of the present invention, a CJT-055 electrodialysis apparatus (manufacturer: Chang Jo Tech. Co.) including a cartridge to which one cation exchange membrane was additionally applied to 10 pairs of ion exchange membranes was used.

1 is a conceptual diagram showing the principle of the concentration or dilution of ions through ion movement in an electrodialysis apparatus including a plurality of ion exchange membranes, and FIG. 2 is a schematic diagram showing a general configuration of such an electrodialysis apparatus and a cell configuration in a cartridge .

As shown in Figure 2, the entire system is a cartridge (AC-220-550, NEOSEPTA CSESE) including a pair of cation exchange membranes and anion exchange membranes (drawing symbol ④), an electrode tank (drawing symbol ③), It includes a dilute tank (drawing symbol ①) and a concentration tank (drawing symbol ②), and although not indicated in the drawing, a rectifier, pump, etc. may be further included. The rectifier usually operates in the range of DC, voltage 0~30V, current 0~5A, but the upper limit of current for device protection is 3A, and it is common to adopt constant voltage and constant current method.

The characteristics of the Cation Exchange Membrane (CSE) and the Anion Exchange Membrane (ASE) that can be used in the electrodialysis apparatus according to the present invention are shown in Table 2.

Cation Exchange Membrane (CSE) Anion Exchange Membrane (ASE) type Strong acid (Na type) Strong base (Cl type) Electrical resistance 1.8 (Ωcm ² ) 2.6(Ωcm ² ) thickness 0.16 (mm) 0.15 (mm) characteristic High mechanical strength Bursting strength ≥0.35 (MPa) Temperature ≤40 (℃) pH 0-14

Example 1: Electrodialysis effect according to volume ratio change

Electrodialysis was performed in a high volume ratio concentration (HVRC) method, and the electrodialysis effect according to the volume ratio change was confirmed.

500 mL of the lithium-containing raw material solution having the composition of Table 1 was added to the concentration chamber, and the volume ratio was changed as shown in Table 3 to the dilution chamber in an amount of 500 to 5000 mL, and a 0.3M Na ₂ SO ₄ solution was added to the electrode chamber. 500 mL was added.

Electrodialysis was started by applying a DC voltage of 10V between the anode and the cathode, and when the electrical conductivity of the dilution chamber was 1.0 mS/cm or less, the electrodialysis was terminated, and the time required was measured.

The solution recovered from the concentration chamber was analyzed with ICP-OES (model name: Optima™ 4300 DV, manufacturer: PerkinElmer) to determine the concentration of ions contained in the solution, and the results are shown in Table 3.

Volume ratio
(V _D /V _C ) Ion concentration in the concentration chamber (g/L) Process time
(minute) Li ⁺ Na ⁺ SO ₄ ^2- Raw material solution 3.3 60.0 179.0 - 1 of 1 4.1 78.8 191.7 230 3 of 1 5.3 101.0 293.2 320 5 of 1 5.3 101.3 234.0 395 7 of 1 5.3 107.4 254.8 395 9 of 1 4.4 72.1 173.1 410 10 of 1 4.1 74.1 155.8 420

As can be seen in Table 3, as the volume ratio (V _D /V _C ) increased, the concentration of lithium in the concentration chamber increased, but at the volume ratio of 9/1 or higher, the concentration of lithium in the concentration chamber decreased. It is believed that this is because the electrolytic osmosis phenomenon is excessive at a volume ratio of 9/1 or more, so that the water permeation rate is faster than the salt permeation rate, and thereby the concentration of lithium decreases. Considering that the process time decreases when the volume ratio increases by 9/1 or more, the volume ratio (V _D /V _C ) is set to 1/1 to 5/1, preferably 2/1 to 4/1, more preferably 3 You can choose from around /1.

3A is a diagram showing the change in lithium concentration in the resulting concentrate when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 4/1 at electrode voltages 8V and 10V. It can be seen that a higher lithium concentration can be obtained at this 10V.

3B is a diagram showing the change in lithium concentration in the resulting concentrate when electrodialysis was performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at the electrode voltage of 10V, and the volume ratio was approximately 3 When it is /1 to 7/1, it can be seen that a higher lithium concentration can be obtained.

4 shows electricity measured every 15 minutes in the concentration chamber (C) and the dilution chamber (D) when electrodialysis was performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at 10V electrode voltage. It is a diagram showing the change in conductivity.

Example 2: Effect according to electrode solution concentration

Electrodialysis was carried out in the same manner as in Example 1, but 500 mL of the raw material solution was each added to the concentration chamber and the dilution chamber at a volume ratio of 1:1, and the Na ₂ SO ₄ solution was added to the electrode chamber in an amount of 500 mL. Was put into.

The solution recovered from the concentration chamber was analyzed by ICP-OES (model name: Optima™ 4300 DV, manufacturer: PerkinElmer) to measure the concentration of ions contained in the solution, and the results are shown in Table 4.

Electrode solution concentration
(M) Ion concentration in the concentration chamber (g/L) Process time
(minute) Li ⁺ Na ⁺ SO ₄ ^2- Raw material solution (comparative) 3.3 60.0 179.0 - 0.1 3.4 124.5 167.6 205 0.2 3.4 114.2 158.9 165 0.3 3.7 114.0 175.0 135 0.5 3.7 114.0 170.0 130 0.7 4.5 119.2 201.5 125 1.0 4.2 102.4 193.7 115

As can be seen in Table 4, as the concentration of the electrode solution Na ₂ SO ₄ increased, the concentration of lithium in the concentration chamber increased, and the process time was shortened. In consideration of the fact that the electrode solution hardly causes any loss during electrodialysis, it is effective to select the concentration of the electrode solution at 0.5M or more, preferably around 0.7M.

Example 3: Concentration of lithium by multistage electrodialysis

Multistage electrodialysis was performed by repeating the electrodialysis of the raw material solution three times.

In the concentration chamber and the dilution chamber, 300 mL and 900 mL of a raw material solution were added in a volume ratio of 1:3, respectively, and 500 mL of a 0.7M Na ₂ SO ₄ solution was added to the electrode chamber. A DC power of 10V was applied between the positive electrode and the negative electrode as an electrode voltage, and the first stage electrodialysis was performed until the electrical conductivity of the dilution chamber became 1.0 mS/cm or less.

After the first stage electrodialysis, the concentrate recovered in the concentration chamber was used as a raw material solution for the second stage electrodialysis, and the second stage electrodialysis was performed under the same conditions as in the first stage electrodialysis.

After the two-stage electrodialysis, the concentrate recovered in the concentration chamber was used as a raw material solution for three-stage electrodialysis, and three-stage electrodialysis was performed under the same conditions as in the first-stage electrodialysis.

After the 3-stage electrodialysis, the concentrated solution recovered from the concentration chamber was analyzed with ICP-OES (model name: Optima ^TM 4300 DV, manufacturer: PerkinElmer) to measure the concentration of ions contained in the solution, and the results are shown in Table 5. .

Electrodialysis recovery Ion concentration in the concentration chamber (g/L) Process time
(minute) Li ⁺ Na ⁺ SO ₄ ^2- Raw material solution (comparative) 3.3 60.0 179.0 - 1st stage 4.9 42.1 147.9 210 2nd stage 6.4 58.3 213.9 270 3-tier 6.9 63.6 224.8 320

As can be seen in Table 5, the concentration of lithium concentrated in the concentration chamber increased as the multistage electrodialysis was repeated. By carrying out electrodialysis in the first stage (i.e., once), the second stage (i.e., repeating twice) and the third stage (i.e., three times, 4.9 g/L, 6.4 g/L and 6.9 g/L of lithium solution respectively Resulted.

Since the lithium concentration of the raw material solution increased while using these as the raw material solution in the next stage, the process time also tended to be longer to 201 minutes, 270 minutes and 320 minutes, respectively.

Test case

In order to examine the concentration rate according to voltage under constant voltage conditions, a lithium-containing raw material solution was added to the dilution chamber and the concentration chamber, and 400 ml of a 0.3 M Na ₂ SO ₄ solution was added to the electrode chamber, respectively, and electrodialysis was started by applying a constant voltage. , The electrical conductivity over time was measured.

When the electrical conductivity of the dilution chamber reached 1.00 mS/cm, electrodialysis was terminated, and the resulting concentrate and diluted solution were analyzed with ICP-OES (model name: Optima ^TM 4300 DV, manufacturer: PerkinElmer) to measure ion concentration.

As a result of concentrating lithium by electrodialysis by applying a DC power of 8 V between the anode and the cathode, it took a total of 3.2 hours, the water recovery rate was 24.75%, the lithium concentration rate was 99.16%, and the energy consumption was 37.52 kWh/m. ³ , the average flow rate was 1.91 mol/m ² h.

As a result of concentrating lithium by electrodialysis by applying a 10 V DC power supply between the anode and the cathode, it took a total of 2.2 hours, the water recovery rate was 29.75%, the lithium concentration rate was 102.0%, and the energy consumption was 45.23 kWh/m ³ , The average flow rate was 2.96 mol/m ² h.

As a result of concentrating lithium by electrodialysis by applying a 12 V DC power supply between the positive electrode and the negative electrode, it took a total of 1.7 hours, the water recovery rate was 35.00%, the lithium concentration rate was 107.34%, and the energy consumption was 53.88 kWh/m ³ , The average flow rate was 3.97 mol/m ² h.

5 is a diagram showing energy consumption when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at the electrode voltage of 10V. As the volume ratio increases, the energy consumption increases. Can be seen.

Attached Figure 6 is a diagram showing the average flow rate when electrodialysis is performed while changing the volume ratio (V _D /V _C ) from 1/1 to 10/1 at the electrode voltage of 10V. As the volume ratio increases, the average flow rate decreases. Can be seen.

In this test example, the water recovery rate, the lithium concentration rate, the average energy consumption and the average flow rate were determined as follows.

(1) Water recovery ratio can be obtained by Equation 1:

[Equation 1]

(Wherein, W represents the water recovery rate (%), V ₀ and V _t represent the volume (L) of the diluted solution after 0 and t minutes, respectively.)

(2) Lithium concentration ratio (Concentration ratio: C _r (%)) can be obtained by Equation 2 below:

[Equation 2]

(In the above formula, C ₀ and C _t are the ion concentrations (mg/L) in the concentrated solution before and after electrodialysis, respectively.)

(3) Average energy consumption (E(kWh/m ³ )) can be obtained by Equation 3:

[Equation 3]

(In the above formula, U(V) is the applied voltage, I(A) is the applied current, and V(L) is the volume of the initial lithium solution.)

(4) Average flux: J (mol/m ² h)) can be obtained by Equation 4:

[Equation 4]

(In the above formula, m is the mass of Li concentrated in the concentrated solution (g), N is the number of pairs of alternately located cation exchange membranes and anion exchange membranes, A is the effective area of the ion exchange membrane (m ² ), M is the concentrated lithium Molecular weight (g/mol), t represents the dialysis time (hr).)

Until now, specific examples of the method for concentrating lithium by electrodialysis according to the present invention have been described, but it is obvious that various implementation modifications are possible within the limits not departing from the scope of the present invention.

Therefore, the scope of the present invention is limited to the described embodiments and should not be defined, and should be defined by the claims and equivalents as well as the claims to be described later.

That is, it should be understood that the above-described embodiments are illustrative in all respects and not limiting, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and All changes or modified forms derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

Claims (12)

In an electrodialysis apparatus comprising an electrode chamber, a dilution chamber, and a concentration chamber formed by alternating one or more pairs of cation exchange membranes and anion exchange membranes between the anode and the cathode, lithium ions are separated by electrodialysis of a solution containing lithium ions. As a method for concentrating lithium by electrodialysis, comprising the following steps:
(Step 1) In the dilution chamber and the concentration chamber, a lithium ion-containing solution at a concentration of 1.0 g/L or more as a raw material solution is added in a volume ratio of 1:1 to 10:1, and 0.1 to 1.0 M Na ₂ as an electrode solution in the electrode chamber. Injecting an SO ₄ solution; And
(Step 2) electrodialysis by applying a DC voltage of 8V to 12V between the anode and the cathode;
It characterized in that it comprises a, the method of concentrating lithium by electrodialysis.
The method of claim 1,
A method for concentrating lithium by electrodialysis, characterized in that at least one pair of cation exchange membranes and anion exchange membranes are alternately disposed between the anode and the cathode, and then one cation exchange membrane is further disposed.
The method of claim 1,
The method of concentrating lithium by electrodialysis, characterized in that the cation exchange membrane and the anion exchange membrane are alternately arranged in at least 5 pairs.
The method of claim 1,
The raw material solution is a method of concentrating lithium by electrodialysis, characterized in that supplied to the dilution chamber and the concentration chamber in a volume ratio of 1:1 to 10:1 in a predetermined total volume.
The method of claim 1 or 4,
The raw material solution is a method of concentrating lithium by electrodialysis, characterized in that it is introduced into the dilution chamber and the concentration chamber in a volume ratio of 2:1 to 7:1.
The method of claim 1,
A method of concentrating lithium by electrodialysis, characterized in that 0.2 to 0.8M Na ₂ SO ₄ solution is added as an electrode solution to the electrode chamber.
The method of claim 1,
The cation exchange membrane is a monovalent cation exchange membrane, characterized in that, the lithium concentration method by electrodialysis.
The method of claim 1,
The electrodialysis is characterized in that it is carried out until the electrical conductivity of the dilution chamber is 1.0 mS / cm or less, the method of concentrating lithium by electrodialysis.
The method of claim 1,
The lithium ion concentration method by electrodialysis, characterized in that the solution containing lithium ions contains lithium at a concentration of 2.0 g/L or more.
The method of claim 1,
The lithium ion-containing solution is a lithium battery waste liquid, characterized in that, the lithium concentration method by electrodialysis.
The method of claim 1,
(Step 3) Injecting the concentrate recovered in the concentration chamber in Step 2 into the raw material solution of Step 1; characterized in that it further comprises, the method of concentrating lithium by electrodialysis.
The method of claim 10,
A method for concentrating lithium by electrodialysis, characterized in that repeating the process including Step 1, Step 2 and Step 3 2 to 5 times.

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