WO2024250140A1 - Use of lithium ferrocyanide, anolyte, and method for extracting lithium from salt lake brine by means of electrical de-intercalation - Google Patents

Abstract

The present disclosure belongs to the technical field of lithium extraction from brine, and particularly relates to the use of lithium ferrocyanide, an anolyte, and a method for extracting lithium from salt lake brine by means of electrical de-intercalation. The method comprises extracting lithium from salt lake brine by means of electrical de-intercalation by using a salt lake brine electrical de-intercalation lithium extraction device. The salt lake brine electrical de-intercalation lithium extraction device comprises an electrolytic bath, an anion exchange membrane, an anode and a cathode, wherein the anion exchange membrane is arranged in the electrolytic bath to vertically divide the electrolytic bath into a cathode chamber and an anode chamber; the anode is arranged in the anode chamber; and the cathode is arranged in the cathode chamber. A voltage is applied to the cathode and the anode, so as to carry out lithium extraction by means of electrical de-intercalation, and an anolyte is added into the anode chamber during the process of lithium extraction by means of electrical de-intercalation. In the present disclosure, by means of adding lithium ferrocyanide into an anode chamber as an anolyte, the intercalation amount of a cathode ion sieve can be guaranteed, such that the lithium de-intercalation capacity of the cathode and the anode is more matched, and the lithium extraction efficiency is improved.

Description

Application of lithium ferrocyanide, anolyte and salt lake brine electro-deintercalation and lithium extraction method Technical Field

The present disclosure relates to the technical field of lithium extraction from brine, and in particular to the application of lithium ferrocyanide, an anolyte and a method for extracting lithium by electro-deintercalation from salt lake brine.

Background Art

The extraction and recovery methods of lithium resources from salt lake brine include electrodialysis, evaporation crystallization, solvent extraction, precipitation, ion exchange and adsorption. Among them, the adsorption method has low cost and high efficiency. However, acid washing is required to produce secondary waste during the exchange and adsorption process, and the permeability and solubility of the adsorbent are poor, which seriously limits its industrial application. The solvent extraction method has high yield, simple operation, and is easy to scale up industrially, but this method uses a large amount of organic solvents, which can easily lead to environmental pollution and equipment corrosion. Traditional lithium extraction methods have the disadvantages of high cost, high energy consumption, and low separation efficiency. Electrodeintercalation is a new research direction for lithium extraction from salt lakes and is a green and efficient lithium extraction technology from salt lakes.

Electrochemical lithium extraction is developed based on the working principle of lithium iron phosphate batteries. The specific application idea is: using the reverse working principle of aqueous lithium battery deintercalation, in essence, the lithium ions in the solution are intercalated into the cathode material for subsequent processing, using the lithium battery positive electrode material with a "memory effect" on lithium ions as the electrode material, salt lake brine as the cathode electrolyte, and a magnesium-free supporting electrolyte as the anode electrolyte, thus forming an electrochemical deintercalation system of "lithium-rich adsorption material | supporting electrolyte | anion membrane | brine | lithium-deficient adsorption material". During the electrolysis process, the cathode obtains electrons to undergo a reduction reaction, so that the lithium ions in the salt lake brine are embedded in the cathode material, thereby achieving separation, and then through subsequent processing and separation operations, the effect of efficient lithium extraction is finally achieved.

CN102382984B discloses a method for electro-deintercalation and lithium extraction using a "rocking chair" electrode system (LiFePO ₄ /FePO ₄ ): the electrolytic cell is divided into two compartments by an anion selective exchange membrane: the LiFePO ₄ electrode is placed in a recovery solution (0.5 mol/L NaCl), and the FePO ₄ is placed in a raw material solution (lithium-containing brine). Under the electric field, the LiFePO ₄ anode undergoes an oxidation (lithium removal) reaction, and the cathode undergoes a reduction (lithium insertion) reaction. In this process, the anions (Cl ^- ) in the raw material solution will migrate across the anion exchange membrane in the middle to the recovery solution.

For an ideal lithium extraction reaction, the cathode will embed a lithium ion while the anode releases a lithium ion. However, in the actual reaction process, the cathode lithium embedding process is affected by the viscosity of the brine and the lithium ion concentration in the solution, resulting in a slower cathode lithium embedding process than the anode lithium de-lithiation process, leading to a mismatch between the de-lithiation and embedding capacities of the cathode and cathode. In particular, when the operating voltage is increased, the difference in the rates of lithium de-intercalation and lithium embedding between the cathode and cathode increases. When using the LiFePO ₄ -FePO ₄ system for lithium extraction, because the two electrodes need to constantly exchange their polarity, this determines that the electrode materials coated on the cathode and cathode need to be as consistent as possible, so it is impossible to match the capacity of the cathode and cathode by improving the electrodes. CN115818801A discloses a method for using a Pb- _FePO4 system for electric deintercalation and lithium extraction, using _FePO4 as the cathode and Pb as the anode to adsorb lithium in brine, and then replacing the brine to remove lithium ions, which can make the capacity of lithium deintercalation and lithium insertion of the anode and cathode more matched, but the lithium extraction process needs to be divided into two steps of lithium insertion and lithium deintercalation, which complicates the lithium extraction process and affects the efficiency of lithium extraction.

In view of this, the present disclosure is proposed.

Summary of the invention

The purpose of the present disclosure includes providing the use of lithium ferrocyanide in preparing an anolyte for lithium electrolysis and deintercalation in salt lake brine.

The purpose of the present disclosure includes providing the use of lithium ferrocyanide in preparing an anolyte for reducing the difference in lithium deintercalation rates between the cathode and the anode in the electro-deintercalation of lithium from lake brine.

The purpose of the present disclosure also includes providing an anolyte for lithium electrolysis and extraction from salt lake brine.

The purpose of the present disclosure also includes providing a method for extracting lithium by electro-deintercalation of salt lake brine.

The purpose of the present disclosure also includes providing a method for recovering salt lake brine.

In order to achieve at least one of the above-mentioned objectives of the present disclosure, the following technical solutions may be adopted:

In a first aspect, the present disclosure provides the use of lithium ferrocyanide in preparing an anolyte for lithium electro-deintercalation and extraction from salt lake brine.

In a second aspect, the present disclosure provides the use of lithium ferrocyanide in the preparation of an anolyte for reducing the difference in lithium deintercalation rates between the cathode and the anode in the electro-deintercalation of lithium from lake brine.

In some embodiments of the present disclosure, the lithium ferrocyanate is added into the anode chamber of a salt lake brine electro-deintercalation lithium extraction system.

In some embodiments of the present disclosure, the concentration of the lithium ferrocyanate in the anolyte is 0.05-1 mol/L.

In some embodiments of the present disclosure, the concentration of the lithium ferrocyanate in the anolyte is 0.2-0.5 mol/L.

In some embodiments of the present disclosure, the anolyte further comprises a supporting electrolyte.

In some embodiments of the present disclosure, the supporting electrolyte includes lithium chloride.

In some embodiments of the present disclosure, the concentration of lithium chloride in the anolyte is 40-60 mmol/L.

In a third aspect, the present disclosure provides an anolyte for lithium electrolysis and extraction from salt lake brine, the components of which include lithium ferrocyanate.

In some embodiments of the present disclosure, the concentration of the lithium ferrocyanate in the anolyte is 0.05-1 mol/L.

In some embodiments of the present disclosure, the components further include a supporting electrolyte.

In some embodiments of the present disclosure, the supporting electrolyte includes lithium chloride.

In some embodiments of the present disclosure, the concentration of lithium chloride in the anolyte is 40-60 mmol/L.

In a fourth aspect, the present disclosure provides a method for extracting lithium by electro-deintercalation of salt lake brine, comprising:

The salt lake brine is subjected to electro-deintercalation and lithium extraction by using a salt lake brine electro-deintercalation and lithium extraction device, the salt lake brine electro-deintercalation and lithium extraction device comprising an electrolytic cell, an anion exchange membrane, an anode and a cathode, the anion exchange membrane is placed in the electrolytic cell to vertically divide the electrolytic cell into a cathode chamber and an anode chamber, the anode is placed in the anode chamber, and the cathode is placed in the cathode chamber;

A voltage is applied to the cathode and the anode to perform electro-deintercalation and lithium extraction. During the electro-deintercalation and lithium extraction process, the anode chamber is filled with the anode electrolyte for electro-deintercalation and lithium extraction of salt lake brine as described in any of the above embodiments.

In some embodiments of the present disclosure, the lithium ferrocyanate is added to the anode chamber before or during the process of lithium electro-extraction.

In some embodiments of the present disclosure, the voltage applied to the cathode and the anode is 0.4-0.8V.

In some embodiments of the present disclosure, the time for the lithium electrolysis is 2-6 hours.

In some embodiments of the present disclosure, after the lithium electro-deintercalation is completed, the positions of the cathode and the anode are swapped, a voltage is applied, and the above steps are repeated until lithium is enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

In some embodiments of the present disclosure, the concentration of lithium in the lithium-rich solution is 3.5-4.1 g/L.

In some embodiments of the present disclosure, the salt lake brine includes lithium-containing brine.

In some embodiments of the present disclosure, the salt lake brine includes one or more of sulfate brine, chloride brine and carbonate brine.

In some embodiments of the present disclosure, the cathode includes at least one of FePO ₄ , Li _1-x Mn ₂ O ₄ , Li _1-x Ni _1/3 Co _1/3 Mn _1/3 O _{2 ,} and Li _7-x Ti ₅ O ₁₂ .

In some embodiments of the present disclosure, the anode includes at least one of LiFePO ₄ , LiMn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , and Li ₇ Ti ₅ O ₁₂ .

In a fifth aspect, the present disclosure provides a method for resource recovery of salt lake brine, which includes the method for electro-deintercalation and extraction of lithium from salt lake brine as described in any of the above-mentioned embodiments.

Compared with the prior art, the beneficial effects of the present invention include:

Since the lithium extraction reaction is carried out using the LiFePO ₄ -FePO ₄ electrode system in the "rocking chair" type electrochemical lithium extraction system, the lithium de-lithiation rate of LiFePO ₄ is significantly faster than the lithium insertion rate of FePO _4. The greater the difference between the lithium de-insertion rates of the cathode and anode, the more mismatched the lithium insertion and de-lithium capacity will be, especially when treating low-concentration lithium-containing solutions. The present disclosure provides a new application of lithium ferrocyanate, by adding lithium ferrocyanate Li ₄ Fe(CN) ₆ as an anode electrolyte into the anode chamber. As the electrical de-insertion time increases, the Li ₄ Fe(CN) ₆ in the anode chamber undergoes an oxidation reaction when powered on, Fe(CN ₆ ) ^4- →Fe(CN ₆ ) ^3- , resulting in a reduction in the amount of lithium ions released from the anode, thereby ensuring that the cathode FePO ₄ can fully insert lithium. Fully ensure the adsorption capacity of the electrode, reduce the problem of capacity mismatch, and improve the recovery rate of lithium.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

FIG1 is a diagram showing the working principle of the method for extracting lithium from salt lake brine by electro-deintercalation provided in the present invention.

DETAILED DESCRIPTION

The embodiments of the present disclosure will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present disclosure and should not be considered to limit the scope of the present disclosure. Where specific conditions are not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased commercially.

The endpoints and any values of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

In a first aspect, the present disclosure provides a new application of lithium ferrocyanide. Specifically, the present disclosure provides the application of lithium ferrocyanide in preparing an anolyte for lithium electro-deintercalation and extraction from salt lake brine.

In the present disclosure, lithium ferrocyanate is purchased from the market, and the manufacturer is Hunan Hanrun Materials Development Co., Ltd. The present disclosure found that when lithium ferrocyanate is added to the anode chamber as the anode electrolyte in the electro-deintercalation and extraction of lithium from lake brine, it can undergo an oxidation reaction during the electro-deintercalation process to reduce the amount of lithium ions released from the anode, thereby reducing the difference in lithium deintercalation rates between the cathode and the anode, and at the same time can also reduce the capacity difference between lithium deintercalation and lithium insertion.

In the present disclosure, lithium ferrocyanide is dissolved in the solution of the anode chamber to form a lithium ferrocyanide solution. The concentration of lithium ferrocyanide in the anolyte is 0.05-1 mol/L, and optionally, the concentration of lithium ferrocyanide in the anolyte is 0.2-0.5 mol/L. In certain embodiments, the concentration of lithium ferrocyanide in the anolyte can be, for example, 0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1 mol/L, any one of them or a range value between any two of them.

In this regard, the present application also provides an anolyte for extracting lithium from salt lake brine by electro-deintercalation, wherein the component includes lithium ferrocyanate, and the concentration of lithium ferrocyanate in the anolyte is 0.05-1 mol/L. In some embodiments, the concentration of lithium ferrocyanate in the anolyte can be, for example, 0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 Any one of 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1 mol/L or a range value between any two of them.

In certain embodiments, the components further include a supporting electrolyte, the supporting electrolyte includes lithium chloride, and the concentration of lithium chloride in the anolyte is 40-60 mmol/L.

Corresponding to the above application, the present disclosure also provides a method for extracting lithium by electro-deintercalation of salt lake brine, which comprises the following steps:

S1. Formation of electrode system.

The anode and cathode are selected to form an electrode system, and the electrolytic cell is vertically divided into a cathode chamber and an anode chamber by an anion exchange membrane.

The present disclosure can be applied to a variety of electrode systems, including but not limited to LiFePO ₄ /FePO ₄ , LiMn ₂ O ₄ /Li _1-x Mn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ /Li _1-x Ni _1/3 Co _1/3 Mn _1/3 O ₂ , Li ₇ Ti ₅ O ₁₂ /Li _7-x Ti ₅ O ₁₂ , etc. Specifically, the cathode includes at least one of FePO ₄ , Li _1-x Mn ₂ O ₄ , Li _1-x Ni _1/3 Co _1/3 Mn _1/3 O ₂ and Li _7-x Ti ₅ O ₁₂ , wherein x represents a lithium-deficient state. The anode includes at least one of LiFePO ₄ , LiMn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and Li ₇ Ti ₅ O ₁₂ . In the present disclosure, the anion exchange membrane is a monovalent selective anion exchange membrane, which is commercially available from Suzhou Shengernuo Technology Co., Ltd.

S2. Adding solution.

Salt lake brine to be extracted with lithium is added into the cathode chamber, and supporting electrolyte and lithium ferrocyanate are added into the anode chamber. Lithium ferrocyanate can be added into the anode chamber before or during the start of the electro-deintercalation and lithium extraction.

The salt lake brine may be any lithium-containing salt lake brine, mainly targeting high magnesium-lithium ratio brine. Salt lake brine includes but is not limited to one or more of sulfate brine, chloride brine and carbonate brine. In some embodiments of the present disclosure, the composition of the salt lake brine includes 0.21-0.47 g/L Li ⁺ , 69.3 g/L Na ⁺ , 111.20 g/L Mg ²⁺ , 6.43 g/L K ⁺ , 2.99 g/L Ca ²⁺ , 8.24 g/L SO ₄ ^2- .

The supporting electrolyte includes lithium chloride, and the concentration of lithium chloride is 40-60 mmol/L.

The concentration of the lithium ferrocyanide solution is 0.05-1 mol/L. In some embodiments, the concentration of the lithium ferrocyanide solution can be, for example, 0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1 mol/L, any one of them or a range value between any two of them.

S3. Electro-deintercalation and lithium extraction.

A voltage is applied to the cathode and the anode for lithium electrolysis. The applied voltage is 0.4-0.8V, and the time for lithium electrolysis is 2-6h.

In some embodiments, the applied voltage may be, for example, any one of 0.4 V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, or a range between any two thereof. The time for the electro-deintercalation of lithium is any one of 2 h, 3 h, 4 h, 5 h, 6 h, or a range between any two thereof.

S4. Exchange electrode positions.

After the lithium extraction is completed, the positions of the cathode and the anode are swapped, voltage is applied, and the above steps are repeated until lithium is enriched from the cathode chamber to the anode chamber to form a lithium-rich solution with a lithium concentration of 3.5-4.1 g/L.

Please refer to Figure 1. The lithium extraction process involved in the present disclosure mainly includes: under the action of the electric field, the _LiFePO4 anode releases lithium ions into the anode electrolyte (lithium ferrocyanate + supporting electrolyte) to form _FePO4 , and at the same time, the _FePO4 cathode absorbs lithium ions in the lithium-containing brine to form _LiFePO4 ; the anode and cathode are exchanged and the above process is repeated to enrich the lithium in the salt lake brine from the cathode chamber to the anode chamber. In the present disclosure, by adding lithium ferrocyanate to the anode chamber, as the electrical deintercalation time increases, the _Li4Fe (CN) ₆ in the anode chamber undergoes an oxidation reaction when powered on, Fe( _CN6 ) ^4- →Fe( _CN6 ) ^3- , resulting in a reduction in the amount of lithium ions released from the anode, ensuring that the cathode _FePO4 can fully embed lithium, fully ensuring the adsorption capacity of the electrode, reducing the capacity mismatch problem, and improving the lithium recovery rate.

The present invention discloses a method for recovering resources of salt lake brine, which comprises the above-mentioned method for extracting lithium by electro-deintercalation of salt lake brine.

The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

Example 1

This embodiment provides a method for extracting lithium by electro-deintercalation of salt lake brine, which comprises the following steps:

(1) LiFePO ₄ is used as the anode, and FePO ₄ after delithiation of LiFePO ₄ is used as the cathode. The anode and cathode are separated into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

(2) The cathode chamber is injected with salt lake brine to be extracted with lithium, and Li ₄ Fe(CN) ₆ and supporting electrolyte (lithium chloride) are added to the anode chamber. The Li ₄ Fe(CN) ₆ solution and lithium chloride are used together as the anode electrolyte.

The composition of the brine is: 0.47g/L Li ⁺ , 69.3g/L Na ⁺ , 111.20g/L Mg ²⁺ , 6.43g/L K ⁺ , 2.99g/L Ca ²⁺ , and 8.24g/L SO ₄ ^2- .

The concentration of Li ₄ Fe(CN) ₆ in the anolyte is 0.3 mol/L, and the concentration of lithium chloride is 50 mmol/L.

(3) A voltage of 0.6 V was applied across the cathode and anode, and the electrical deintercalation time was 4 h.

(4) At the end of the reaction, after the two electrodes have completed their corresponding insertion/extraction processes, the two electrodes are swapped and the above process is repeated once. The reaction is stopped when the current drops to 0.3 mA, and lithium is enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

Example 2

This embodiment provides a method for extracting lithium by electro-deintercalation of salt lake brine, which comprises the following steps:

(1) LiFePO ₄ is used as the anode, and FePO ₄ after delithiation of LiFePO ₄ is used as the cathode. The anode and cathode are separated into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

(2) The cathode chamber is injected with salt lake brine to be extracted with lithium, and Li ₄ Fe(CN) ₆ and supporting electrolyte (lithium chloride) are added to the anode chamber. The Li ₄ Fe(CN) ₆ solution and lithium chloride are used together as the anode electrolyte.

The composition of brine is: 0.47g/L Li ⁺ , 69.3g/L Na ⁺ , 111.20g/L Mg ²⁺ , 6.43g/L K ⁺ , 2.99g/L Ca ²⁺ , 8.24 g/L SO ₄ ^2- .

The concentration of Li ₄ Fe(CN) ₆ in the anolyte is 0.5 mol/L, and the concentration of lithium chloride is 50 mmol/L.

(3) A voltage of 0.4 V was applied across the cathode and anode, and the electrical deintercalation time was 6 h.

(4) At the end of the reaction, after the two electrodes have completed their corresponding insertion/extraction processes, the two electrodes are swapped and the above process is repeated once. The reaction is stopped when the current drops to 0.3 mA, and lithium is enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

Embodiment 3:

This embodiment provides a method for extracting lithium by electro-deintercalation of salt lake brine, which comprises the following steps:

(1) LiFePO ₄ is used as the anode, and FePO ₄ after delithiation of LiFePO ₄ is used as the cathode. The anode and cathode are separated into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

(2) The cathode chamber is injected with salt lake brine to be extracted with lithium, and Li ₄ Fe(CN) ₆ and supporting electrolyte (lithium chloride) are added to the anode chamber. The Li ₄ Fe(CN) ₆ solution and lithium chloride are used together as the anode electrolyte.

The composition of the brine is: 0.47g/L Li ⁺ , 69.3g/L Na ⁺ , 111.20g/L Mg ²⁺ , 6.43g/L K ⁺ , 2.99g/L Ca ²⁺ , and 8.24g/L SO ₄ ^2- .

The concentration of Li ₄ Fe(CN) ₆ in the anolyte is 0.05 mol/L, and the concentration of lithium chloride is 50 mmol/L.

(3) A voltage of 0.8 V was applied across the cathode and anode, and the electrical deintercalation time was 2 h.

(4) At the end of the reaction, after the two electrodes have completed their corresponding insertion/extraction processes, the two electrodes are swapped and the above process is repeated once. The reaction is stopped when the current drops to 0.3 mA, and lithium is enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

Embodiment 4:

This embodiment provides a method for extracting lithium by electro-deintercalation of salt lake brine, which comprises the following steps:

(1) LiFePO ₄ is used as the anode, and FePO ₄ after delithiation of LiFePO ₄ is used as the cathode. The anode and cathode are separated into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

(2) The cathode chamber is injected with salt lake brine from which lithium is to be extracted, and the anode chamber is added with lithium chloride solution as the anode electrolyte.

The composition of the brine is: 0.47g/L Li ⁺ , 69.3g/L Na ⁺ , 111.20g/L Mg ²⁺ , 6.43g/L K ⁺ , 2.99g/L Ca ²⁺ , and 8.24g/L SO ₄ ^2- .

The concentration of lithium chloride in the anolyte was 50 mmol/L.

(3) A voltage of 0.8 V was applied across the cathode and anode. After the electro-deintercalation reaction had been going on for 3 h, Li ₄ Fe(CN) ₆ was added to the anode chamber solution. The concentration of Li ₄ Fe(CN) ₆ in the anode electrolyte was 0.35 mol/L, and the electrolysis was continued for 1 h.

(4) When the reaction is over, the two electrodes are swapped after completing their corresponding insertion/extraction processes. Then repeat the above process once, and stop the reaction when the current drops to 0.3 mA, so that lithium can be enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

Example 5

The difference between this embodiment and embodiment 1 is that the voltage applied for electrical deintercalation in step (3) is 0.4 V, and the other steps are the same as those in embodiment 1.

Example 6

The difference between this embodiment and embodiment 1 is that the voltage applied for electrical deintercalation in step (3) is 0.8 V, and the other steps are the same as those in embodiment 1.

Example 7

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 0.1 mol/L, and the other steps are the same as those in embodiment 1.

Example 8

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 0.2 mol/L, and the other steps are the same as those in embodiment 1.

Example 9

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 0.4 mol/L, and the other steps are the same as those in embodiment 1.

Example 10

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 0.5 mol/L, and the other steps are the same as those in embodiment 1.

Embodiment 11

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 0.6 mol/L, and the other steps are the same as those in embodiment 1.

Example 12

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 0.8 mol/L, and the other steps are the same as those in embodiment 1.

Example 13

The difference between this embodiment and embodiment 1 is that the concentration of Li ₄ Fe(CN) ₆ in step (3) is 1 mol/L, and the other steps are the same as those in embodiment 1.

Embodiment 14

The difference between this embodiment and embodiment 1 is that the concentration of lithium chloride in step (3) is 40 mol/L, and the other steps are Same as Example 1.

Embodiment 15

The difference between this embodiment and embodiment 1 is that the concentration of lithium chloride in step (3) is 60 mol/L, and the other steps are the same as those in embodiment 1.

Example 16

The difference between this embodiment and embodiment 1 is that in step (1), LiMn ₂ O ₄ is used as the anode and Li _1-x Mn ₂ O ₄ is used as the cathode. The other steps are the same as those in embodiment 1.

Embodiment 17

The difference between this embodiment and embodiment 1 is that the composition of the brine in step (2) is: 0.47 g/L Li ⁺ , 69.3 g/L Na ⁺ , 111.20 g/L Mg ²⁺ , 6.43 g/L K ⁺ , 2.99 g/L Ca ²⁺ , 8.24 g/L SO ₄ ^2- .

Comparative Example 1

This comparative example is substantially the same as Example 1, except that in step (3) of this comparative example, Li ₄ Fe(CN) ₆ is not added into the anode chamber, but only lithium chloride solution (the concentration of lithium chloride is 50 mmol/L) is added. The other steps are the same as Example 1.

Comparative Example 2

This comparative example is substantially the same as Example 1, except that in step (3) of this comparative example, only Li ₄ Fe(CN) ₆ is added into the anode chamber, wherein the concentration of Li ₄ Fe(CN) ₆ is 0.3 mol/L, and no lithium chloride solution is added. The other steps are the same as Example 1.

Comparative Example 3

This comparative example is substantially the same as Example 1, except that in step (3) of this comparative example, the concentration of Li ₄ Fe(CN) ₆ added into the anode chamber is 0.01 mol/L.

Comparative Example 4

This comparative example is substantially the same as Example 1, except that in step (3) of this comparative example, the concentration of Li ₄ Fe(CN) ₆ added into the anode chamber is 1.5 mol/L.

Comparative Example 5

The difference between this embodiment and embodiment 1 is that the voltage applied for electrical deintercalation in step (3) is 0.2 V, and the other steps are the same as those in embodiment 1.

Comparative Example 6

The difference between this embodiment and embodiment 1 is that the voltage applied for electrical deintercalation in step (3) is 1.0 V, and the other steps are the same as those in embodiment 1.

Comparative Example 7

This comparative example is basically the same as Example 1, except that in step (3) of this comparative example, the anode chamber Li ₄ Fe(CN) ₆ was added to replace potassium sulfate.

Performance testing:

The main indicators of lithium extraction obtained after lithium extraction experiments on the electrodes obtained in the examples and comparative examples are shown in the following table.

The lithium recovery rate is calculated as (C ₀ -C _e )/C ₀ × 100%, where _{C 0} is the initial lithium ion concentration of the brine, measured in g/L; and _Ce is the lithium ion concentration of the brine after electrolysis, measured in g/L.

The concentration of the obtained lithium-rich solution is calculated by direct detection.

The calculation method of electrode adsorption capacity is adsorption capacity q = V (C ₀ -C _e ) / m. V is the volume of brine, with a unit volume of 1L; C ₀ is the initial brine lithium ion concentration, with a unit of g/L; _Ce is the brine lithium ion concentration after electrolysis, with a unit of g/L; m is the mass of the electrode material, with a unit weight of 1g.

It can be found from Example 1, Examples 5-6 and Comparative Examples 5 and 6 that the adsorption capacity of the electrode decreases when the voltage is too large or too small. This is because the voltage is too small and the electrode lithium extraction efficiency is too low, and the voltage is too large, resulting in excessive inhibition of lithium release by Fe(CN6) ^3- oxidation.

It can be seen from Example 1, Examples 7-13 and Comparative Examples 3-4 that when the concentration of Li ₄ Fe(CN) ₆ is controlled at 0.2-0.5 mol/L, it is more conducive to increasing the adsorption capacity of the electrode.

It can be seen from Example 1 and Examples 14-15 that when the concentration of lithium chloride is within the range disclosed herein, the lithium extraction index is not much different.

It can be seen from Example 1 and Examples 16-17 that the method provided by the present disclosure is applicable to a variety of electrode systems and a variety of brines.

It can be seen from Example 1 and Comparative Example 1 that adding Li ₄ Fe(CN) ₆ to the recovery liquid can significantly increase the adsorption capacity of the electrode, thereby increasing the concentration of lithium in the recovery liquid and improving the lithium recovery rate. This shows that adding Li ₄ Fe(CN) ₆ to the anode can ensure the embedding amount of the cathode ion sieve, thereby making the capacity of the anode and cathode for lithium deintercalation more matched and improving the lithium extraction efficiency.

It can be seen from Example 1 and Comparative Example 2 that when only Li ₄ Fe(CN) ₆ is used as the anolyte, the ionization equilibrium constant of Li ₄ Fe(CN) ₆ alone is not high, resulting in a lithium extraction index that is significantly lower than that in Example 1. In the example, using Li ₄ Fe(CN) ₆ and a supporting electrolyte together as the anolyte can improve the conductivity of the solution, thereby increasing the lithium extraction efficiency.

It can be seen from Example 1 and Comparative Example 7 that when other reagents are selected to replace Li ₄ Fe(CN) ₆ , the effect is significantly worse than that of Example 1.

In summary, in the "rocking chair" type electrochemical lithium extraction system, the LiFePO ₄ -FePO ₄ electrode system is used for lithium extraction reaction, and the lithium removal rate of LiFePO ₄ is significantly faster than the lithium insertion rate of FePO _4. The greater the difference between the lithium deinsertion rates of the cathode and cathode, the more mismatched the capacity of lithium insertion and deinsertion will be, especially when treating low-concentration lithium-containing solutions. The present disclosure provides a new application of lithium ferrocyanate, by adding lithium ferrocyanate Li ₄ Fe(CN) ₆ as an anode electrolyte into the anode chamber, with the increase of the electrical deinsertion time, the Li ₄ Fe(CN) ₆ in the anode chamber undergoes an oxidation reaction under power-on, Fe(CN ₆ ) ^4- →Fe(CN ₆ ) ^3- , resulting in a reduction in the amount of lithium ions released from the anode, ensuring that the cathode FePO ₄ can fully embed lithium, fully ensuring the adsorption capacity of the electrode, reducing the capacity mismatch problem, and improving the lithium recovery rate.

The optional implementation modes of the present disclosure are described in detail above, but the present disclosure is not limited thereto. Within the technical concept of the present disclosure, the technical solution of the present disclosure can be subjected to a variety of simple modifications, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present disclosure and belong to the protection scope of the present disclosure.

Industrial Applicability

Since the lithium extraction reaction is carried out by using the LiFePO ₄ -FePO ₄ electrode system in the "rocking chair" type electrochemical lithium extraction system, the lithium de-lithiation rate of LiFePO ₄ is significantly faster than the lithium insertion rate of FePO _4. The greater the difference between the lithium de-insertion rate of the cathode and cathode, the more the problem of mismatch between the lithium insertion and de-lithiation capacity will be caused, especially when treating low-concentration lithium-containing solutions. The present disclosure provides a new application of lithium ferrocyanate, by adding lithium ferrocyanate Li ₄ Fe(CN) ₆ as an anode electrolyte into the anode chamber, with the increase of the electrical de-insertion time, the Li ₄ Fe(CN) ₆ in the anode chamber undergoes an oxidation reaction under power-on, Fe(CN ₆ ) ^4- →Fe(CN ₆ ) ^3- , resulting in a reduction in the amount of lithium ions released from the anode, ensuring that the cathode FePO ₄ can fully insert lithium, fully ensuring the adsorption capacity of the electrode, reducing the problem of capacity mismatch, and improving the recovery rate of lithium.

Claims (24)

Application of lithium ferrocyanate in the preparation of anolyte for lithium electrolysis and extraction from salt lake brine. Application of lithium ferrocyanate in the preparation of an anolyte for reducing the difference in lithium deintercalation rates between the cathode and the anode in the electro-deintercalation of lithium from lake brine. The use according to claim 1 or 2 is characterized in that the lithium ferrocyanate is added to the anode chamber of the salt lake brine electro-deintercalation and lithium extraction system. The use according to claim 1 or 2, characterized in that the concentration of the lithium ferrocyanate in the anolyte is 0.05-1 mol/L. The use according to claim 1 or 2, characterized in that the concentration of the lithium ferrocyanate in the anolyte is 0.2-0.5 mol/L. The use according to claim 1 or 2, characterized in that the anolyte further comprises a supporting electrolyte. The use according to claim 6 is characterized in that the supporting electrolyte comprises lithium chloride. The use according to claim 7, characterized in that the concentration of the lithium chloride in the anolyte is 40-60 mmol/L. An anolyte for lithium extraction from salt lake brine by electro-deintercalation is characterized in that its components include lithium ferrocyanate. The anolyte for lithium extraction from salt lake brine by electro-deintercalation according to claim 9, characterized in that the concentration of lithium ferrocyanate in the anolyte is 0.05-1 mol/L. The anolyte for lithium extraction from salt lake brine according to any one of claims 9-10 is characterized in that the components also include a supporting electrolyte. The anolyte for lithium electrolysis from salt lake brine according to claim 11, wherein the supporting electrolyte comprises lithium chloride. The anolyte for lithium extraction from salt lake brine by electro-deintercalation according to claim 12, characterized in that the concentration of lithium chloride in the anolyte is 40-60 mmol/L. A method for extracting lithium by electro-deintercalation of salt lake brine, characterized in that it comprises: The salt lake brine is subjected to electro-deintercalation and lithium extraction by using a salt lake brine electro-deintercalation and lithium extraction device, the salt lake brine electro-deintercalation and lithium extraction device comprising an electrolytic cell, an anion exchange membrane, an anode and a cathode, the anion exchange membrane is placed in the electrolytic cell to vertically divide the electrolytic cell into a cathode chamber and an anode chamber, the anode is placed in the anode chamber, and the cathode is placed in the cathode chamber; A voltage is applied to the cathode and the anode to perform electro-deintercalation and lithium extraction. During the electro-deintercalation and lithium extraction process, the anode chamber is filled with an anode electrolyte for electro-deintercalation and lithium extraction from salt lake brine as described in any one of claims 9 to 13. The method for electro-deintercalation and lithium extraction from salt lake brine according to claim 14 is characterized in that the lithium ferrocyanide is added to the anode chamber before or during the electro-deintercalation and lithium extraction. The method for extracting lithium from salt lake brine by electro-deintercalation according to any one of claims 14-15, characterized in that the voltage applied to the cathode and the anode is 0.4-0.8V. The method for extracting lithium from salt lake brine by electro-deintercalation according to any one of claims 14 to 16, characterized in that the time for electro-deintercalation and lithium extraction is 2 to 6 hours. The method for electro-deintercalation and lithium extraction from salt lake brine according to any one of claims 14 to 17 is characterized in that, after the electro-deintercalation and lithium extraction is completed, it also includes swapping the positions of the cathode and the anode, applying voltage, and repeating the above steps until lithium is enriched from the cathode chamber to the anode chamber to form a lithium-rich solution. The method for extracting lithium by electro-deintercalation of salt lake brine according to claim 18, characterized in that the concentration of lithium in the lithium-rich solution is 3.5-4.1 g/L. The method for extracting lithium by electro-deintercalation of salt lake brine according to any one of claims 14 to 19, characterized in that the salt lake brine comprises lithium-containing brine. The method for extracting lithium by electro-deintercalation of salt lake brine according to any one of claims 14 to 20 is characterized in that the salt lake brine comprises one or more of sulfate brine, chloride brine and carbonate brine. The method for extracting lithium by electro-deintercalation of salt lake brine according to any one of claims 14 to 21, characterized in that the cathode comprises at least one of FePO ₄ , Li _1-x Mn ₂ O ₄ , Li _1-x Ni _1/3 Co _1/3 Mn _1/3 O ₂ and Li _7-x Ti ₅ O ₁₂ . The method for extracting lithium by electro-deintercalation of salt lake brine according to any one of claims 14 to 22, characterized in that the anode comprises at least one of LiFePO ₄ , LiMn ₂ O ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and Li ₇ Ti ₅ O ₁₂ . A method for recovering lithium from salt lake brine, characterized in that it comprises the method for extracting lithium from salt lake brine by electro-deintercalation according to any one of claims 14 to 23.