Application of lithium ferrocyanide, anolyte and method for extracting lithium from salt lake brine by electro-deintercalation

Abstract

The present disclosure belongs to the technical field of lithium extraction from brine, and particularly relates to application of lithium ferrocyanide, anode electrolyte and a method for lithium extraction from salt lake brine by electro-deintercalation, which comprises the following steps: using a lithium extraction device for salt lake brine electro-deintercalation to extract lithium from salt lake brine, wherein the lithium extraction device for salt lake brine electro-deintercalation comprises an electrolytic cell, an anion exchange membrane, an anode and a cathode, the anion exchange membrane is arranged in the electrolytic cell to vertically divide the electrolytic cell 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; and applying voltage to the cathode and the anode to extract lithium by electro-deintercalation, wherein an anode electrolyte is added to the anode chamber during the lithium extraction by electro-deintercalation. The present disclosure can ensure the embedding amount of the cathode ion sieve by adding lithium ferrocyanide as an anode electrolyte to the anode chamber, so that the lithium extraction capacity of the cathode and the anode is more matched, and the lithium extraction efficiency is improved.

Description

Technical Field

[0001] This disclosure relates to the field of lithium extraction technology from brine, and more specifically, to the application of lithium ferrocyanate, anolyte, and a method for lithium extraction by electro-deintercalation and intercalation from salt lake brine. Background Technology

[0002] Methods for extracting and recovering lithium resources from salt lake brine include electrodialysis, evaporation crystallization, solvent extraction, precipitation, ion exchange, and adsorption. Among these, adsorption is relatively low-cost and highly efficient. However, the adsorption process requires acid washing, generating secondary waste, and the adsorbent's poor permeability and solubility severely limit its industrial application. Solvent extraction offers high yields, is simple to operate, and is easily scaled up industrially; however, this method uses large amounts of organic solvents, which can easily lead to environmental pollution and equipment corrosion. Traditional lithium extraction methods suffer from high costs, high energy consumption, and low separation efficiency. Electro-deintercalation / extraction is a new research direction for lithium extraction from salt lakes, representing a green and efficient lithium extraction technology.

[0003] Electrochemical lithium extraction is developed based on the working principle of lithium iron phosphate batteries. The specific application approach is to utilize the reverse working principle of lithium-ion battery deintercalation in aqueous solutions. Essentially, it involves embedding lithium ions in the cathode material for further processing. A lithium-ion battery cathode material with a "memory effect" is used as the electrode material, brine from a salt lake is used as the cathode electrolyte, and a magnesium-free supporting electrolyte is used as the anode electrolyte, thus forming an electrochemical deintercalation system consisting of "lithium-rich adsorbent material | supporting electrolyte | anion exchange membrane | brine | lithium-deficient adsorbent material". During electrolysis, the cathode gains electrons and undergoes a reduction reaction, causing lithium ions in the brine to embed into the cathode material, thus achieving separation. Subsequent processing further separates the lithium ions, ultimately achieving efficient lithium extraction.

[0004] CN102382984B discloses a method for electro-delithiation and intercalation of lithium using a "rocking chair" electrode system (LiFePO4 / FePO4): The electrolytic cell is divided into two compartments by an anion-selective exchange membrane: the LiFePO4 electrode is placed in a recovery solution (0.5 mol / L NaCl), and the FePO4 is placed in a feed solution (lithium-containing brine). Under an electric field, the LiFePO4 anode undergoes oxidation (delithiation) and the cathode undergoes reduction (lithiation). During this process, the anions (Cl-) in the feed solution... - They will cross the intermediate anion exchange membrane and migrate into the recovery solution.

[0005] For an ideal lithium extraction reaction, a lithium ion is extracted from the anode while a lithium ion is inserted into the cathode. However, in actual reactions, the cathode lithium insertion process is affected by the viscosity of the brine and the concentration of lithium ions in the solution, causing the cathode lithium insertion process to be slower than the anode delithiation process. This leads to a mismatch between the lithium extraction and insertion capacities of the anode and cathode, especially as the operating voltage increases, the difference in the lithium extraction and insertion rates between the anode and cathode widens. Using the LiFePO4-FePO4 system for lithium extraction requires constant switching of electrode polarities, necessitating that the electrode materials coated on the anode and cathode be kept as consistent as possible. Therefore, it is impossible to design a capacity-matched anode and cathode by modifying the electrodes. CN115818801A discloses a method for electro-deintercalation and lithium extraction using a Pb-FePO4 system. Using FePO4 as the cathode and Pb as the anode, lithium is adsorbed from the brine, and then the brine is replaced for lithium ion extraction. This method can achieve a better match between the lithium extraction and insertion capacities of the anode and cathode. However, the lithium extraction process needs to be divided into two steps: lithium insertion and deintercalation, which complicates the process and affects the efficiency of lithium extraction.

[0006] In view of this, this disclosure is hereby made. Summary of the Invention

[0007] The purpose of this disclosure includes providing the application of lithium ferrocyanate as an anolyte in the preparation of lithium electrolytically extracted from salt lake brine.

[0008] The purpose of this disclosure includes providing the application of lithium ferrocyanate in the preparation of an anolyte for reducing the lithium deintercalation / intercalation rate difference between the cathode and anode in lithium electro-deintercalation from lake brine.

[0009] The purpose of this disclosure also includes providing an anolyte for the electrolytic extraction of lithium from salt lake brine.

[0010] The purpose of this disclosure also includes providing a method for the electro-deintercalation and extraction of lithium from salt lake brine.

[0011] The purpose of this disclosure also includes providing a method for resource recovery from salt lake brine.

[0012] To achieve at least one of the above-mentioned objectives of this disclosure, the following technical solutions may be adopted:

[0013] In one aspect, this disclosure provides the application of lithium ferrocyanate as an anolyte in the preparation of lithium electrolytic extraction from salt lake brine.

[0014] Secondly, this disclosure provides the application of lithium ferrocyanate in the preparation of an anolyte for reducing the difference in lithium deintercalation rates between the cathode and anode in lithium electro-deintercalation from lake brine.

[0015] In some embodiments of this disclosure, the lithium ferrocyanate is added to the anode chamber of a brine electro-deintercalation lithium extraction system.

[0016] In some embodiments of this disclosure, the concentration of lithium ferrocyanate in the anolyte is 0.05-1 mol / L.

[0017] In some embodiments of this disclosure, the concentration of lithium ferrocyanate in the anolyte is 0.2-0.5 mol / L.

[0018] In some embodiments of this disclosure, the anolyte further includes a supporting electrolyte.

[0019] In some embodiments of this disclosure, the supporting electrolyte includes lithium chloride.

[0020] In some embodiments of this disclosure, the concentration of lithium chloride in the anolyte is 40-60 mmol / L.

[0021] Thirdly, this disclosure provides an anolyte for the electrolytic extraction of lithium from salt lake brine, the components of which include lithium ferrocyanate.

[0022] In some embodiments of this disclosure, the concentration of lithium ferrocyanate in the anolyte is 0.05-1 mol / L.

[0023] In some embodiments of this disclosure, the components also include a supporting electrolyte.

[0024] In some embodiments of this disclosure, the supporting electrolyte includes lithium chloride.

[0025] In some embodiments of this disclosure, the concentration of lithium chloride in the anolyte is 40-60 mmol / L.

[0026] Fourthly, this disclosure provides a method for the electro-deintercalation and extraction of lithium from salt lake brine, comprising:

[0027] A lithium electro-deintercalation and extraction device for salt lake brine is used to perform lithium electro-deintercalation and extraction from salt lake brine. The device includes an electrolytic cell, an anion exchange membrane, an anode, and a cathode. The anion exchange membrane is placed in the electrolytic cell, which vertically divides 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.

[0028] A voltage is applied to the cathode and the anode to perform electro-deintercalation and extraction of lithium. During the electro-deintercalation and extraction of lithium, the anode electrolyte for electro-deintercalation and extraction of lithium from salt lake brine as described in any of the preceding embodiments is added to the anode chamber.

[0029] In some embodiments of this disclosure, the lithium ferrocyanate is added to the anode chamber before or during the electro-deintercalation of lithium.

[0030] In some embodiments of this disclosure, the voltage applied to the cathode and the anode is 0.4-0.8V.

[0031] In some embodiments of this disclosure, the time for the electro-deintercalation and extraction of lithium is 2-6 hours.

[0032] In some embodiments of this disclosure, after the electro-deintercalation and extraction of lithium 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.

[0033] In some embodiments of this disclosure, the lithium concentration in the lithium-rich solution is 3.5-4.1 g / L.

[0034] In some embodiments of this disclosure, the salt lake brine includes lithium-containing brine.

[0035] In some embodiments of this disclosure, the salt lake brine includes one or more of sulfate-type brine, chloride-type brine, and carbonate-type brine.

[0036] In some embodiments of this disclosure, the cathode includes FePO4 and Li. 1-x Mn2O4, Li 1-x Ni 1 / 3 Co 1 / 3 Mn 1 / 3O2 and Li 7-x Ti5O 12 At least one of them.

[0037] In some embodiments of this disclosure, the anode includes LiFePO4, LiMn2O4, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and Li7Ti5O 12 At least one of them.

[0038] Fifthly, this disclosure provides a method for resource recovery from 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 embodiments.

[0039] Compared with the prior art, the beneficial effects of this disclosure include:

[0040] In the "rocking chair" electrochemical lithium extraction system, using a LiFePO4-FePO4 electrode system, the delithiation rate of LiFePO4 is significantly faster than the lithium insertion rate of FePO4. A greater difference in the lithium insertion / extraction rates between the anode and cathode leads to a mismatch between the lithium insertion and extraction capacities, especially when processing low-concentration lithium-containing solutions. This disclosure provides a novel application of lithium ferrocyanide. By adding lithium ferrocyanide (Li4Fe(CN)6) as the anolyte to the anode chamber, as the electro-intercalation / extraction time increases, the Li4Fe(CN)6 in the anode chamber undergoes an oxidation reaction under energized conditions, resulting in Fe(CN6)2. 4- →Fe(CN6) 3- This results in a reduction in the amount of lithium ions extracted from the anode, ensuring that FePO4 at the cathode can fully intercalate lithium, thus guaranteeing the adsorption capacity of the electrode, reducing capacity mismatch, and improving lithium recovery rate. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram illustrating the working principle of the lithium extraction method from salt lake brine provided in this disclosure. Detailed Implementation

[0043] The embodiments of this disclosure will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this disclosure. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0044] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein.

[0045] In a first aspect, this disclosure provides a new application of lithium ferrocyanate. Specifically, this disclosure provides the application of lithium ferrocyanate as an anolyte in the preparation of lithium electrolytic extraction from salt lake brine.

[0046] In this disclosure, lithium ferrocyanide was purchased commercially from Hunan Hanrun Materials Development Co., Ltd. The research in this disclosure found that adding lithium ferrocyanide as an anode electrolyte to the anode chamber during the electro-deintercalation and deintercalation of lithium in lake brine can cause it to undergo an oxidation reaction during the electro-deintercalation and deintercalation process to reduce the amount of lithium ions extracted from the anode, thereby reducing the difference in lithium deintercalation and deintercalation rates between the cathode and the anode, and also reducing the capacity difference between lithium deintercalation and lithium intercalation.

[0047] In this disclosure, lithium ferrocyanide is dissolved in the solution in the anode chamber to form a lithium ferrocyanide solution. The concentration of lithium ferrocyanide in the anolyte is 0.05-1 mol / L, optionally, the concentration of lithium ferrocyanide in the anolyte is 0.2-0.5 mol / L. In some embodiments, the concentration of lithium ferrocyanide in the anolyte can be, for example, any one or a range between any two of 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, and 1 mol / L.

[0048] In this regard, this application also provides an anolyte for the electro-extraction and intercalation of lithium from salt lake brine, the components of which include lithium ferrocyanide. The concentration of lithium ferrocyanide in the anolyte is 0.05-1 mol / L. In some embodiments, the concentration of lithium ferrocyanide in the anolyte can be, for example, any one or a range between any two of 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, and 1 mol / L.

[0049] In some embodiments, the components also include a supporting electrolyte, which includes lithium chloride, and the concentration of lithium chloride in the anolyte is 40-60 mmol / L.

[0050] Corresponding to the above-mentioned applications, this disclosure also provides a method for the electro-deintercalation and extraction of lithium from salt lake brine, which includes the following steps:

[0051] S1, Formation of the electrode system.

[0052] 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 using an anion exchange membrane.

[0053] This disclosure is applicable to a variety of electrode systems, including but not limited to LiFePO4 / FePO4 and LiMn2O4 / Li1-x Mn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 / Li 1-x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, Li7Ti5O 12 / Li 7-x Ti5O 12 Wait, specifically, the cathode includes FePO4, Li 1-x Mn2O4, Li 1-x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and Li 7-x Ti5O 12 At least one of the following, where x represents a lithium-deficient state. The anode includes LiFePO4, LiMn2O4, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and Li7Ti5O 12 At least one of the following. In this disclosure, the anion exchange membrane is a monovalent selective anion exchange membrane, which is commercially available and purchased from Suzhou Shengernuo Technology Co., Ltd.

[0054] S2, addition of solution.

[0055] The brine from the salt lake from which lithium is to be extracted is added to the cathode chamber, and the supporting electrolyte and lithium ferrocyanate are added to the anode chamber. The lithium ferrocyanate can be added to the anode chamber before or during the electro-deintercalation and extraction of lithium.

[0056] The brine can be any lithium-containing brine, but is primarily targeted at brines with a high magnesium-to-lithium ratio. The brine includes, but is not limited to, one or more of sulfate-type, chloride-type, and carbonate-type brines. In some embodiments of this disclosure, the brine composition includes 0.21-0.47 g / L Li. + 69.3 g / L Na + 111.20 g / L Mg 2+ 6.43g / LK + 2.99 g / L Ca 2+ 8.24 g / L SO4 2- .

[0057] Supporting electrolytes include lithium chloride, with a concentration of 40-60 mmol / L.

[0058] The concentration of the lithium ferrocyanate solution is 0.05-1 mol / L. In some embodiments, the concentration of the lithium ferrocyanate solution can be, for example, any one or a range between any two of 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, and 1 mol / L.

[0059] S3, Electrolytic deintercalation of lithium.

[0060] Lithium electro-deintercalation is performed by applying voltage to the cathode and anode. The applied voltage is 0.4-0.8V, and the electro-deintercalation time is 2-6 hours.

[0061] In some implementations, 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. The electro-deintercalation / extraction time is any one of 2 h, 3 h, 4 h, 5 h, 6 h, or a range between any two.

[0062] S4. Change electrode positions.

[0063] After the electro-deintercalation and extraction of lithium is completed, the positions of the cathode and 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, forming a lithium-rich solution with a lithium concentration of 3.5-4.1 g / L.

[0064] Please see Figure 1 The lithium extraction process disclosed herein mainly includes: under the action of an electric field, the LiFePO4 anode releases lithium ions into the anolyte (lithium ferrocyanate + supporting electrolyte) to form FePO4, while the FePO4 cathode absorbs lithium ions from the lithium-containing brine to form LiFePO4; by exchanging the anode and cathode and repeating the above process, lithium in the brine can be enriched from the cathode chamber to the anode chamber. In this disclosure, by adding lithium ferrocyanate to the anode chamber, as the electro-deintercalation time increases, Li4Fe(CN)6 in the anode chamber undergoes an oxidation reaction under energized conditions, resulting in Fe(CN6). 4- →Fe(CN6) 3- This results in a reduction in the amount of lithium ions extracted from the anode, ensuring that FePO4 at the cathode can fully intercalate lithium, thus guaranteeing the adsorption capacity of the electrode, reducing capacity mismatch, and improving lithium recovery rate.

[0065] This disclosure provides a resource recovery method for salt lake brine, which includes the above-mentioned method for electro-deintercalation and extraction of lithium from salt lake brine.

[0066] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0067] Example 1

[0068] This embodiment provides a method for lithium extraction from salt lake brine by electro-deintercalation and intercalation, which includes the following steps:

[0069] (1) LiFePO4 is used as the anode and FePO4 after delithiation of LiFePO4 is used as the cathode. The anode and cathode are divided into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

[0070] (2) The brine of the salt lake to be extracted is injected into the cathode chamber, and Li4Fe(CN)6 and supporting electrolyte (lithium chloride) are added to the anode chamber. The Li4Fe(CN)6 solution and lithium chloride are used together as the anode electrolyte.

[0071] The brine composition is: 0.47 g / L Li + 69.3 g / L Na + 111.20 g / L Mg 2+ 6.43 g / LK + 2.99 g / L Ca 2+ 8.24 g / L SO4 2- .

[0072] The concentration of Li4Fe(CN)6 in the anolyte was 0.3 mol / L, and the concentration of lithium chloride was 50 mmol / L.

[0073] (3) Apply a voltage of 0.6V to both ends of the cathode and anode, and the electric deintercalation time is 4h.

[0074] (4) When the reaction ends, after the two electrodes have completed their respective insertion / extraction processes, the positions of the two electrodes are swapped, and the above process is repeated once. When the current drops to 0.3mA, the reaction is stopped, and lithium can be enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

[0075] Example 2

[0076] This embodiment provides a method for lithium extraction from salt lake brine by electro-deintercalation and intercalation, which includes the following steps:

[0077] (1) LiFePO4 is used as the anode and FePO4 after delithiation of LiFePO4 is used as the cathode. The anode and cathode are divided into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

[0078] (2) The brine of the salt lake to be extracted is injected into the cathode chamber, and Li4Fe(CN)6 and supporting electrolyte (lithium chloride) are added to the anode chamber. The Li4Fe(CN)6 solution and lithium chloride are used together as the anode electrolyte.

[0079] The brine composition is: 0.47 g / L Li + 69.3 g / L Na + 111.20 g / L Mg 2+ 6.43 g / LK + 2.99 g / L Ca 2+ 8.24 g / L SO4 2- .

[0080] The concentration of Li4Fe(CN)6 in the anolyte was 0.5 mol / L, and the concentration of lithium chloride was 50 mmol / L.

[0081] (3) Apply a voltage of 0.4V to both ends of the cathode and anode, and the electric deintercalation time is 6h.

[0082] (4) When the reaction ends, after the two electrodes have completed their respective insertion / extraction processes, the positions of the two electrodes are swapped, and the above process is repeated once. When the current drops to 0.3mA, the reaction is stopped, and lithium can be enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

[0083] Example 3:

[0084] This embodiment provides a method for lithium extraction from salt lake brine by electro-deintercalation and intercalation, which includes the following steps:

[0085] (1) LiFePO4 is used as the anode and FePO4 after delithiation of LiFePO4 is used as the cathode. The anode and cathode are divided into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

[0086] (2) The brine of the salt lake to be extracted is injected into the cathode chamber, and Li4Fe(CN)6 and supporting electrolyte (lithium chloride) are added to the anode chamber. The Li4Fe(CN)6 solution and lithium chloride are used together as the anode electrolyte.

[0087] The brine composition is: 0.47 g / L Li + 69.3 g / L Na + 111.20 g / L Mg 2+ 6.43 g / LK + 2.99 g / L Ca 2+ 8.24 g / L SO4 2- .

[0088] The concentration of Li4Fe(CN)6 in the anolyte was 0.05 mol / L, and the concentration of lithium chloride was 50 mmol / L.

[0089] (3) Apply a voltage of 0.8V to both ends of the cathode and anode, and the electric deintercalation time is 2h.

[0090] (4) When the reaction ends, after the two electrodes have completed their respective insertion / extraction processes, the positions of the two electrodes are swapped, and the above process is repeated once. When the current drops to 0.3mA, the reaction is stopped, and lithium can be enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

[0091] Example 4:

[0092] This embodiment provides a method for lithium extraction from salt lake brine by electro-deintercalation and intercalation, which includes the following steps:

[0093] (1) LiFePO4 is used as the anode and FePO4 after delithiation of LiFePO4 is used as the cathode. The anode and cathode are divided into a cathode chamber and an anode chamber by a monovalent selective anion exchange membrane.

[0094] (2) The brine from the salt lake to be extracted is injected into the cathode chamber, and lithium chloride solution is added to the anode chamber as the anode electrolyte.

[0095] The brine composition is: 0.47 g / L Li + 69.3 g / L Na + 111.20 g / L Mg 2+ 6.43 g / LK + 2.99 g / L Ca 2+ 8.24 g / L SO4 2- .

[0096] The concentration of lithium chloride in the anolyte is 50 mmol / L.

[0097] (3) Apply a voltage of 0.8V to both ends of the cathode and anode. After the electro-deintercalation reaction has been carried out for 3 hours, add Li4Fe(CN)6 to the solution in the anode chamber. The concentration of Li4Fe(CN)6 in the anode electrolyte is 0.35mol / L. Continue electrolysis for 1 hour.

[0098] (4) When the reaction ends, after the two electrodes have completed their respective insertion / extraction processes, the positions of the two electrodes are swapped, and the above process is repeated once. When the current drops to 0.3mA, the reaction is stopped, and lithium can be enriched from the cathode chamber to the anode chamber to form a lithium-rich solution.

[0099] Example 5

[0100] The difference between this embodiment and Embodiment 1 is that the voltage applied for electrical de-intercalation in step (3) is 0.4V, while the other steps are the same as in Embodiment 1.

[0101] Example 6

[0102] The difference between this embodiment and Embodiment 1 is that the voltage applied for electrical de-intercalation in step (3) is 0.8V, while the other steps are the same as in Embodiment 1.

[0103] Example 7

[0104] The difference between this embodiment and Example 1 is that the concentration of Li4Fe(CN)6 in step (2) is 0.1 mol / L, while the other steps are the same as in Example 1.

[0105] Example 8

[0106] The difference between this embodiment and Embodiment 1 is that the concentration of Li4Fe(CN)6 in step (2) is 0.2 mol / L, while the other steps are the same as in Embodiment 1.

[0107] Example 9

[0108] The difference between this embodiment and Example 1 is that the concentration of Li4Fe(CN)6 in step (2) is 0.4 mol / L, while the other steps are the same as in Example 1.

[0109] Example 10

[0110] The difference between this embodiment and Example 1 is that the concentration of Li4Fe(CN)6 in step (2) is 0.5 mol / L, while the other steps are the same as in Example 1.

[0111] Example 11

[0112] The difference between this embodiment and Example 1 is that the concentration of Li4Fe(CN)6 in step (2) is 0.6 mol / L, while the other steps are the same as in Example 1.

[0113] Example 12

[0114] The difference between this embodiment and Example 1 is that the concentration of Li4Fe(CN)6 in step (2) is 0.8 mol / L, while the other steps are the same as in Example 1.

[0115] Example 13

[0116] The difference between this embodiment and Example 1 is that the concentration of Li4Fe(CN)6 in step (2) is 1 mol / L, while the other steps are the same as in Example 1.

[0117] Example 14

[0118] The difference between this embodiment and Example 1 is that the concentration of lithium chloride in step (2) is 40 mol / L, while the other steps are the same as in Example 1.

[0119] Example 15

[0120] The difference between this embodiment and Embodiment 1 is that the concentration of lithium chloride in step (2) is 60 mol / L, while the other steps are the same as in Embodiment 1.

[0121] Example 16

[0122] The difference between this embodiment and Embodiment 1 is that in step (1), LiMn2O4 is the anode, and Li 1-x Mn2O4 was used as the cathode, and the other steps were the same as in Example 1.

[0123] Example 17

[0124] 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 / LK + 2.99 g / L Ca 2+ 8.24 g / L SO4 2- .

[0125] Comparative Example 1

[0126] This comparative example is basically the same as Example 1, except that in step (2) of this comparative example, Li4Fe(CN)6 is not added to 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 in Example 1.

[0127] Comparative Example 2

[0128] This comparative example is basically the same as Example 1, except that in step (2) of this comparative example, only Li4Fe(CN)6 is added to the anode chamber, and the concentration of Li4Fe(CN)6 is 0.3mol / L. No lithium chloride solution is added. The other steps are the same as in Example 1.

[0129] Comparative Example 3

[0130] This comparative example is basically the same as Example 1, except that in step (2) of this comparative example, the concentration of Li4Fe(CN)6 added in the anode chamber is 0.01 mol / L.

[0131] Comparative Example 4

[0132] This comparative example is basically the same as Example 1, except that in step (2) of this comparative example, the concentration of Li4Fe(CN)6 added in the anode chamber is 1.5 mol / L.

[0133] Comparative Example 5

[0134] The difference between this embodiment and Embodiment 1 is that the voltage applied for electrical de-intercalation in step (3) is 0.2V, while the other steps are the same as in Embodiment 1.

[0135] Comparative Example 6

[0136] The difference between this embodiment and Embodiment 1 is that the voltage applied for electrical de-intercalation in step (3) is 1.0V, while the other steps are the same as in Embodiment 1.

[0137] Comparative Example 7

[0138] This comparative example is basically the same as Example 1, except that in step (2) of this comparative example, Li4Fe(CN)6 added to the anode chamber is replaced with potassium sulfate.

[0139] Performance testing:

[0140] The main lithium extraction indicators obtained after conducting lithium extraction experiments on the electrodes obtained in the examples and comparative examples are shown in the table below.

[0141]

[0142] The lithium recovery rate is calculated as (C0-C...). e ) / C0×100%. C0 is the initial lithium ion concentration in the brine, measured in g / L; C e The concentration of lithium ions in the brine after electrolysis is expressed in g / L.

[0143] The concentration of the lithium-rich solution was calculated by direct detection.

[0144] The method for calculating the electrode adsorption capacity is: Adsorption capacity q = V(C0 - C) e V is the volume of the brine, with a unit volume of 1 L; C0 is the initial lithium ion concentration in the brine, measured in g / L; C e The concentration of lithium ions in the brine after electrolysis is expressed in g / L; m represents the mass of the electrode material, with a unit weight of 1g.

[0145] Examples 1, 5-6, and Comparative Examples 5 and 6 show that the adsorption capacity of the electrode decreases when the voltage is too high or too low. This is because when the voltage is too low, the lithium extraction efficiency of the electrode is too low, and when the voltage is too high, it leads to Fe(CN6) degradation. 3- Oxidation has an excessively strong inhibitory effect on lithium extraction.

[0146] As can be seen from Examples 1, 7-13 and Comparative Examples 3-4, when the concentration of Li4Fe(CN)6 is controlled at 0.2-0.5 mol / L, it is more conducive to increasing the adsorption capacity of the electrode.

[0147] As can be seen from Examples 1 and 14-15, when the concentration of lithium chloride is within the range disclosed herein, the lithium extraction index does not differ significantly.

[0148] As can be seen from Examples 1 and 16-17, the method provided in this disclosure is applicable to a variety of electrode systems and also to a variety of brines.

[0149] As can be seen from Example 1 and Comparative Example 1, adding Li4Fe(CN)6 to the recovery solution can significantly increase the adsorption capacity of the electrode, thereby increasing the lithium concentration in the recovery solution and improving the lithium recovery rate. This indicates that adding Li4Fe(CN)6 to the anode can ensure the insertion amount of the cathode ion sieve, thereby making the lithium insertion / extraction capacity of the anode and cathode more matched and improving the lithium extraction efficiency.

[0150] As can be seen from Example 1 and Comparative Example 2, when Li4Fe(CN)6 is used as the anolyte alone, the ionization equilibrium constant of Li4Fe(CN)6 is not high, resulting in a lithium extraction index that is significantly lower than that of Example 1. In the examples, using Li4Fe(CN)6 and the supporting electrolyte together as the anolyte can improve the conductivity of the solution, thereby increasing the lithium extraction efficiency.

[0151] As can be seen from Example 1 and Comparative Example 7, when other reagents are used instead of Li4Fe(CN)6, the effect is significantly worse than that of Example 1.

[0152] In summary, in the "rocking chair" electrochemical lithium extraction system, using the LiFePO4-FePO4 electrode system for the lithium extraction reaction, the delithiation rate of LiFePO4 is significantly faster than the lithium insertion rate of FePO4. The greater the difference in lithium insertion / extraction rates between the anode and cathode, the more mismatched the lithium insertion and extraction capacities become, especially when processing low-concentration lithium-containing solutions. This disclosure provides a novel application of lithium ferrocyanide by adding Li4Fe(CN)6 as the anolyte to the anode chamber. As the electro-intercalation / extraction time increases, the Li4Fe(CN)6 in the anode chamber undergoes an oxidation reaction under energized conditions, resulting in Fe(CN6)2. 4- →Fe(CN6) 3- This results in a reduction in the amount of lithium ions extracted from the anode, ensuring that FePO4 at the cathode can fully intercalate lithium, thus guaranteeing the adsorption capacity of the electrode, reducing capacity mismatch, and improving lithium recovery rate.

[0153] The optional embodiments of this disclosure have been described in detail above; however, this disclosure is not limited thereto. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this disclosure and are all within the protection scope of this disclosure.

[0154] Industrial applicability

[0155] In the "rocking chair" electrochemical lithium extraction system, using a LiFePO4-FePO4 electrode system, the delithiation rate of LiFePO4 is significantly faster than the lithium insertion rate of FePO4. A greater difference in the lithium insertion / extraction rates between the anode and cathode leads to a mismatch between the lithium insertion and extraction capacities, especially when processing low-concentration lithium-containing solutions. This disclosure provides a novel application of lithium ferrocyanide. By adding lithium ferrocyanide (Li4Fe(CN)6) as the anolyte to the anode chamber, as the electro-intercalation / extraction time increases, the Li4Fe(CN)6 in the anode chamber undergoes an oxidation reaction under energized conditions, resulting in Fe(CN6)2. 4- →Fe(CN6) 3- This results in a reduction in the amount of lithium ions extracted from the anode, ensuring that FePO4 at the cathode can fully intercalate lithium, thus guaranteeing the adsorption capacity of the electrode, reducing capacity mismatch, and improving lithium recovery rate.

Claims

1. A method for extracting lithium from salt lake brine by electrolysis, characterized in that, It comprises: The lithium is extracted from salt lake brine by using a salt lake brine electro-deintercalation device, the salt lake brine electro-deintercalation device comprises 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. The lithium is extracted by applying a voltage of 0.4-0.8V to the cathode and the anode, and in the process of electro-deintercalation, the anode electrolyte for lithium extraction from salt lake brine is added into the anode chamber, the components of the anode electrolyte include lithium ferrocyanide and lithium chloride, and the concentration of the lithium ferrocyanide in the anode electrolyte is 0.05-1 mol / L.

2. The method according to claim 1, wherein, The concentration of the lithium ferrocyanide in the anode electrolyte is 0.2-0.5 mol / L.

3. The method of claim 1, wherein the salt lake brine is heated to a temperature of about 80°C to about 100°C. The concentration of the lithium chloride in the anode electrolyte is 40-60 mmol / L.

4. The method of claim 1, wherein the salt lake brine is heated to a temperature of about 80°C to about 100°C. The lithium ferrocyanide is added into the anode chamber before or during the process of electro-deintercalation.

5. The method for lithium extraction from salt lake brine by electro-deintercalation according to claim 1, characterized in that, The time of electro-deintercalation is 2-6h.

6. The method of claim 1, wherein the salt lake brine is from the Great Salt Lake. After the electro-deintercalation is completed, the positions of the cathode and the anode are exchanged, a voltage is applied, and the above steps are repeated until the enrichment of lithium from the cathode chamber to the anode chamber is completed, and a lithium-rich liquid is formed.

7. The method of claim 6, wherein the salt lake brine is heated to a temperature of about 80°C to about 100°C. The concentration of lithium in the lithium-rich liquid is 3.5-4.1 g / L.

8. The method of claim 1, wherein the salt lake brine is from the Great Salt Lake. The salt lake brine comprises lithium-containing brine.

9. The method of claim 1, wherein the salt lake brine is from the Great Salt Lake. The salt lake brine comprises one or more of sulfate type brine, chloride type brine and carbonate type brine.

10. The method of claim 1, wherein the salt lake brine is from the Great Salt Lake. The cathode includes at least one of FePO4, Li 1-x Mn2O4, Li 1-x Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, and Li 7-x Ti5O 12 .

11. The method of claim 1, wherein the salt lake brine is from the Great Salt Lake. The anode includes at least one of LiFeP04, LiMn204, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2and Li7Ti50 12 ​ 12. A method for recovering lithium from a salt lake brine, characterized by, It comprises the method for lithium extraction from salt lake brine according to any one of claims 1-11.

Images