A system and method for extracting and concentrating lithium from a lithium-containing solution

Abstract

The present application relates to a system and method for extracting and enriching lithium from a lithium-containing solution, wherein lithium extraction active substances and electron transfer substances are placed in the lithium-containing solution, hydrogen is introduced into the lithium-containing solution, and the following reactions occur: hydrogen transfers electrons to the electron transfer substances; the electron transfer substances transfer the received electrons to the lithium extraction active substances; the lithium extraction active substances adsorb lithium ions in the lithium-containing solution; in the lithium extraction process, pre-lithium extraction active substances and electron transfer substances are placed in the lithium-containing solution, oxygen is introduced into the lithium-containing solution, and the following reactions occur: oxygen obtains the electrons of the electron transfer substances, the electron active substances obtain the electrons on the pre-lithium extraction active substances, and the pre-lithium extraction active substances release lithium ions into the lithium-containing solution; selective lithium extraction and lithium removal are achieved through a catalytic reaction involving gas, no external potential is required, the energy consumption of the lithium extraction and lithium removal process driven by the catalytic reaction is low, gas is involved in lithium extraction and lithium removal, and complex chemical substance separation is avoided.

Description

Technical Field

[0001] This invention relates to a system and method for extracting and enriching lithium from lithium-containing solutions, belonging to the field of lithium ion extraction. Background Technology

[0002] With the development of the lithium battery industry, the development and utilization of lithium resources have received high attention, and ensuring the security of the lithium supply chain is of great significance to my country's strategic development. Currently, my country's lithium reserves are approximately 1.5 million tons of metallic lithium, of which more than 80% of the exploitable lithium resources are stored in salt lakes in Qinghai and Tibet, where development is relatively low. Lithium extraction technology from lithium-containing solutions is an important approach to obtaining lithium resources; however, the lithium content in seawater and salt lake brines is currently very low, while the concentration of interfering ions is high, making lithium extraction and enrichment very challenging.

[0003] For salt lakes in Qinghai Province, characterized by a high magnesium-to-lithium ratio in the brine, the prevailing technology involves lithium extraction from the old brine. The raw brine undergoes sun-drying to remove sodium and potassium, resulting in old brine. During the sun-drying process in the salt fields, a significant amount of lithium is lost, leading to low lithium resource utilization. Furthermore, the sodium and potassium removal process in the salt fields takes several years, necessitating precautions against risks such as seepage, flooding, extreme weather, and dam failure. In magnesium sulfate subtype salt lakes, approximately 60% of the lithium is lost during the preparation of old brine. This substantial lithium loss significantly reduces economic viability. Therefore, developing technologies for direct lithium extraction from raw brine to improve extraction and utilization rates is crucial for ensuring a stable lithium resource supply.

[0004] The salt lakes in Tibet are of higher quality than those in Qinghai and remain largely undeveloped. However, Tibet's high altitude and poor infrastructure pose a challenge to salt lake development. Furthermore, the local ecosystem is fragile, and existing lithium extraction technologies are environmentally unfriendly, characterized by high energy consumption, high reagent consumption, and high costs. This necessitates the development of low-carbon, green lithium extraction technologies. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a system and method for extracting and enriching lithium from a lithium-containing solution. This system or method uses hydrogen as a reducing agent, introduces a lithium-extracting active material into the lithium-containing solution, and utilizes an electron transfer medium to achieve electron transfer between hydrogen and the lithium-extracting active material, thereby enabling lithium ion embedding into the lithium-extracting active material to achieve lithium extraction. Alternatively, it uses oxygen as an oxidizing agent, introduces a pre-delithiation active material into the lithium extraction solution, and utilizes an electron transfer medium to achieve electron transfer between oxygen and the pre-delithiation active material, thereby enabling the pre-delithiation active material to release lithium ions into the lithium extraction solution to achieve lithium extraction.

[0006] On one hand, the present invention provides a system for extracting and enriching lithium from a lithium-containing solution, comprising a lithium-containing solution, a lithium extraction solution, an electron transport substance, a lithium extraction active substance, a pre-delithiation active substance, hydrogen, and oxygen.

[0007] During lithium extraction, the lithium extraction active material and the electron transfer material are placed in the lithium-containing solution, and hydrogen gas is introduced into the lithium-containing solution, resulting in the following reactions: hydrogen gas transfers electrons to the electron transfer material; the electron transfer material transfers the received electrons to the lithium extraction active material; and the lithium extraction active material adsorbs lithium ions in the lithium-containing solution.

[0008] During delithiation, the pre-delithiation active material and the electron transport material are placed in the lithium extraction solution, and oxygen is introduced into the lithium extraction solution, resulting in the following reaction: oxygen acquires electrons from the electron transport material, the electron active material acquires electrons from the pre-delithiation active material, and the pre-delithiation active material releases lithium ions into the lithium extraction solution.

[0009] The pre-delithiation active material is obtained by adsorbing lithium ions onto the lithium extraction active material. The lithium extraction active material after the lithium extraction reaction is removed and either left untreated or treated before being added to the lithium extraction solution as pre-delithiation active material. This treatment can be physical or chemical; chemical treatment aims to better release lithium ions. The lithium extraction active material is obtained after the pre-delithiation active material releases lithium ions. The pre-delithiation active material and the lithium extraction active material are recycled. The electron transfer material can be a catalyst to promote the reaction between the gas and the active material. This system uses a redox reaction as the power source and hydrogen and oxygen as the redox substances to achieve a low-cost, low-energy, and pollution-free lithium extraction method.

[0010] As a preferred embodiment, the pre-delithiation active material is lithium iron phosphate, which is one or a mixture of several of LiFePO4, LixMeyFePO4, LiFexMeyPO4, LiFePO4 / C, LixMeyFePO4 / C, and LiFexMeyPO4 / C, wherein Me is one or a mixture of several of Mn, Co, Mo, Ti, Al, Ni, and Nb, and 0 < x < 1, 0 < y < 1; the lithium extraction active material is iron phosphate. Alternatively, the pre-delithiation active material may be lithium manganese oxide, wherein the lithium manganese oxide is one or a mixture of several of the following: LiMn2O4, LiMnO2, LixMeyMnO2, LiMnxMeyPO4, LiMnO2 / C, LixMeyMnO2 / C, and LiMnxMeyO2 / C, wherein Me is one or a mixture of several of the following: Co, Mo, Ti, Al, Ni, and Nb, and 0 < x < 1, 0 < y < 1; or the pre-delithiation active material may be a ternary metal composite oxide, wherein the ternary metal composite oxide is LiAxByC(1-xy)Oz, wherein A, B, and C are one or a mixture of several of the following: Mn, Co, Mo, Ti, Al, Ni, and Nb, and 0 < x < 1, 0 < y < 1.

[0011] As a preferred embodiment, the electron transport substance in the lithium extraction solution may be the same as or different from the electron transport substance in the lithium-containing solution. The electron transport substance may be one substance or a combination of multiple substances. The electron transport substance in the lithium extraction solution has the property of catalyzing hydrogen oxidation, while the electron transport substance in the lithium-containing solution has the property of catalyzing oxygen reduction. Preferably, the electron transport substances in the lithium extraction solution and the lithium-containing solution are the same. When the active lithium-extraction substance is extracted from the lithium-containing solution, the electron transport substance is simultaneously extracted and placed in the lithium extraction solution for reaction. This allows for simultaneous extraction and transfer, avoiding separation of the two substances. When the electron transport substances are the same in both the lithium extraction solution and the lithium-containing solution, the electron transport substances can be a combination of one or more substances. It can be a single substance that exhibits both catalytic hydrogen oxidation and catalytic oxygen reduction properties, or it can be a combination of multiple substances, each possessing both catalytic hydrogen oxidation and catalytic oxygen reduction properties. These multiple substances can be combined in a way that compensates for each other's weaknesses, such as by different reaction temperatures, catalytic activities, or reaction times. In the case of multiple substances, it can also be a combination of a substance that only exhibits catalytic hydrogen oxidation properties and a substance that only exhibits catalytic oxygen reduction properties. The substance with catalytic hydrogen oxidation properties only functions in the lithium extraction stage, while the substance with catalytic oxygen reduction properties only functions in the delithiation stage.

[0012] As a preferred embodiment, the electron transfer material is a noble metal catalyst or a metal oxide catalyst. The noble metal catalyst includes one or more of the following: platinum-based catalyst (Pt / C), palladium-based catalyst (Pd / C), iridium-based catalyst (Ir / C), ruthenium-based catalyst (Ru nanoparticles), and gold-based catalyst (Au nanoparticles). This type of catalyst has both the characteristics of catalyzing hydrogen oxidation and oxygen reduction.

[0013] The metal or oxide catalysts include Mn-based catalysts, Co-based catalysts, Ni-based catalysts, and Fe-based catalysts. The Mn-based catalyst is Mn or an oxide of Mn; the Co-based catalyst is Co or an oxide of Co; the Ni-based catalyst is Ni or an oxide of Ni; and the Fe-based catalyst is Fe or an oxide of Fe. The Ni-based catalyst exhibits catalytic hydrogen oxidation properties; the Mn-based, Co-based, Fe-based, or Mn-based oxides exhibit catalytic oxygen reduction properties. When using this type of catalyst, catalysts with both hydrogen oxidation and oxygen reduction properties need to be used in combination. The Ni-based catalyst and the Mn-based catalyst can be simultaneously placed in a lithium-containing solution or a lithium extraction solution; the Ni-based catalyst and the Co-based catalyst can be simultaneously placed in a lithium-containing solution or a lithium extraction solution; or the Ni-based catalyst and the Fe-based catalyst can be simultaneously placed in a lithium-containing solution or a lithium extraction solution.

[0014] To accelerate the reaction process and increase the reaction depth, the lithium extraction active material and the pre-delithiation active material in this invention are dispersed in solution in powder or particulate form, or they can be loaded on a mesh substrate in powder or particulate form. The electron transfer material can be solid, liquid, or gas. For ease of recycling, it is preferred to be solid and insoluble in the corresponding solution. Its distribution can be dispersed in solution in powder or particulate form. When hydrogen or oxygen is introduced, it flows in the solution and realizes electron transfer. The specific process is as follows: hydrogen gas is introduced into the solution. The hydrogen gas comes into contact with the electron transfer material (catalyst). The hydrogen gas transfers electrons to the catalyst and generates hydrogen ions. At the same time, the catalyst conducts electrons to the pre-delithiation active material (lithium extraction active material). The pre-delithiation active material is reduced and adsorbs lithium ions in the solution, thus completing the lithium extraction process. During the delithiation process, the pre-delithiated active material and catalyst are dispersed in the solution. Oxygen is introduced into the solution, and when the oxygen comes into contact with the catalyst, it takes electrons from the catalyst and generates hydroxide ions. At the same time, the electron-deficient catalyst takes electrons from the lithium-intercalated active material. As the active material is oxidized, lithium ions are released into the solution, thus completing the lithium enrichment.

[0015] The electron transport material and the lithium extraction active material can be in a separate state, both dispersed in the solution as particles or powder, with electron transfer achieved through water flow, airflow, or their own dynamic movement. Alternatively, they can be bonded together and then dispersed in the solution as particles or powder. Specifically, the electron transport material is attached to the surface of the lithium extraction active material or the pre-delithiation active material, with coating being the preferred attachment method. This structure shortens the electron transport path, accelerates the reaction process, and is beneficial to reaction stability.

[0016] The preferred method for preparing coated active substances is as follows:

[0017] First, add the electron transport substance and Nafion solution to the ethanol solution to allow Nafion and the electron transport substance to come into full contact and form a mixed solution;

[0018] The pre-delithiation active material or lithium extraction active material is added to the mixed solution and thoroughly ground to obtain a well-mixed slurry. The slurry is dried until the ethanol completely evaporates, and the resulting solid is ground into powder using a mortar and pestle to obtain the lithium extraction active material or pre-delithiation active material coated with electron transfer material. After preparation, Nafion binds the electron transfer material to the surface of the active material.

[0019] On the other hand, the present invention provides a method for extracting and enriching lithium from a lithium-containing solution, comprising the following steps: using hydrogen as a reducing agent, using an electron transfer agent to transfer electrons from hydrogen to a lithium-extracting active agent, wherein the lithium-extracting active agent adsorbs lithium ions in the lithium-containing solution;

[0020] Delithiation: Using oxygen as the oxidizing agent, electrons are transferred from the pre-delithiation active material to the oxygen using an electron transfer medium. The pre-delithiation active material releases lithium ions into the lithium extraction solution. The pre-delithiation active material is the product of the lithium extraction active material after extracting lithium ions.

[0021] After lithium extraction is completed, the lithium extraction active material and electron transport material in the lithium-containing solution are obtained and placed in the lithium extraction solution. Oxygen is introduced to remove lithium. After removal, the lithium-containing active material is placed in a new lithium-containing solution to work. The electron transport material and active material are recovered and recycled to achieve energy savings.

[0022] In this invention, the process of transferring electrons from hydrogen to the lithium-extraction active material using an electron transfer substance can be a single-stage reaction or a multi-stage reaction. A single-stage reaction means that only one electron transfer reaction occurs, and the electron transfer substance directly transfers electrons from hydrogen to the lithium-extraction active material after gaining electrons. If it is a multi-stage reaction, the electron transfer substance includes at least two substances, namely a first transfer substance and a second transfer substance. Electrons from hydrogen are transferred to the lithium-extraction active material sequentially through the first transfer substance and the second transfer substance. It can also include a first transfer substance, a second transfer substance, ..., an nth transfer substance. Electrons are transferred from hydrogen to the first transfer substance, then to the second transfer substance, and finally to the nth transfer substance, from which they are transferred to the lithium-extraction active material.

[0023] Similarly, the process of transferring electrons from the pre-delithiated active material to oxygen using an electron transfer medium can be a single-stage, two-stage, or multi-stage reaction. In a single-stage reaction, the electron transfer medium directly transfers electrons from hydrogen to the pre-delithiated active material. In a multi-stage reaction, the electron transfer medium includes a first transfer medium and a second transfer medium; electrons from oxygen are sequentially transferred through the first and second transfer media to the pre-delithiated active material. In another multi-stage reaction, the electron transfer medium consists of the first, second, and so on up to the nth transfer medium; electrons are transferred from the pre-delithiated active material to the nth transfer medium, then to the (n-1)th transfer medium, and finally to the first transfer medium, from which they are transferred to oxygen. Single-stage reactions are advantageous for accelerating the reaction process, while multi-stage reactions are advantageous for controlling the intermediate reaction processes. This invention achieves the reaction between gases or active materials by setting up electron transfer media, which on the one hand promotes the reaction between the two, and on the other hand facilitates the control of the reaction process.

[0024] As a preferred embodiment, the mass ratio of the electron transport material to the lithium extraction active material / pre-delithiation active material is (2-20):100. The two are mixed in a synergistic ratio, which is beneficial to accelerate the reaction process. A further preferred mixing mass ratio is (5-10):100. The lithium extraction active material is FePO4, the pre-delithiation active material is LiFePO4, and the electron transport material is pt / c (platinum supported on activated carbon).

[0025] As a preferred method, the flow rate of hydrogen during lithium extraction is 10-100 ml / min; the flow rate of oxygen during delithiation is 10-100 ml / min. At this flow rate, the gas supply can be guaranteed to ensure the progress of the reaction, while preventing excessive flow rate and gas waste. Hydrogen is introduced during lithium extraction with a purity range of 20%-100%, specifically 20%, 30%, 50%, or 80%, etc. Oxygen is introduced during delithiation with a concentration and purity range of 20%-100%, specifically 20%, 50%, 60%, or 80%, etc.

[0026] The beneficial effects of this invention include: Selective lithium extraction and delithiation are achieved through a gas-participating catalytic reaction, without the need for an external potential; the energy consumption of the catalytically driven lithium extraction and delithiation process is low. Introducing gas into the reaction avoids chemical pollution and complex substance separation.

[0027] In this invention, the pre-delithiation / lithiation active material and catalyst are dispersed in the lithium-containing solution as particles, which greatly increases the contact area between the active material and the lithium-containing solution, and greatly improves the lithium extraction reaction rate and the delithiation reaction rate.

[0028] In this invention, the pre-delithiation active material and the pre-lithiation active material are reduced by real-time chemical reaction, which has high electron utilization rate. It can realize the extraction of lithium from low-concentration lithium-containing solutions (lithium concentration less than 100 ppm) and can directly extract lithium from the original brine, avoiding the loss of lithium during the lithium extraction process.

[0029] In this invention, the catalyst can be repeatedly cycled with the pre-delithiated active material for lithium extraction and delithiation, resulting in a long service life and reduced costs for lithium extraction and enrichment. Attached Figure Description

[0030] Figure 1 Potential curve of hydrogen oxidation reaction under platinum-carbon catalysis;

[0031] Figure 2 Potential curve of lithium ion intercalation reaction of iron phosphate;

[0032] Figure 3 Potential curve of oxygen reduction reaction under platinum-carbon catalysis. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, but it should be understood that the scope of protection of the present invention is not limited to the specific implementation.

[0034] This invention discloses a system for extracting and enriching lithium from a lithium-containing solution, comprising a lithium extraction system and a lithium removal system. In the lithium extraction system, a lithium extraction active material and an electron transport material are placed in the lithium-containing solution. Hydrogen gas is introduced into the solution, and the hydrogen gas transfers electrons to the lithium extraction active material through the electron transport material, achieving lithium adsorption. The electron transport material and the lithium extraction active material are dispersed in the solution as particles or powder. During the reaction, electron transfer is achieved through collisions or other forms of contact between the electron transport material and the lithium extraction active material. The dispersion can be either uniformly dispersed in the solution or the lithium extraction active material is loaded onto a fixed substrate, such as a carbon mesh or metal mesh, while the electron transport material is dispersed in the solution. Alternatively, the electron transport material can exist as a coating structure, with the electron transport material attached to the surface of the lithium extraction active material.

[0035] After lithium extraction, the lithium-intercalated active material is used as the pre-delithiation active material. The pre-delithiation active material and the electron transport material are placed in the lithium extraction solution, and oxygen is introduced to cause the pre-delithiation active material to release lithium ions. The electron transport material can be the electron transport material in the lithium-containing solution or a new material. If it is an electron transport material with a coated structure and the lithium extraction active material, then after the lithium extraction is completed, the lithium extraction active material and the electron transport material are transferred together to the lithium extraction solution.

[0036] The lithium extraction active material and the pre-delithiation active material are recycled. The pre-delithiation active material is lithium iron phosphate, which can be LiFePO4, LixMeyFePO4, LiFexMeyPO4, LiFePO4 / C, LixMeyFePO4 / C, or LiFexMeyPO4 / C, where Me is one of Mn, Co, Mo, Ti, Al, Ni, or Nb, and 0 < x < 1, 0 < y < 1; or it can be lithium manganese oxide, which is LiMn2O4, LiMnO2, LixMeyMnO2, LiMnxMeyPO4, LiMnO2 / C, or LixMey A mixture of one or more of MnO2 / C and LiMnxMeyO2 / C, where Me is one or more of Co, Mo, Ti, Al, Ni, and Nb, 0 < x < 1, 0 < y < 1. It can also be a ternary metal composite oxide, LiAxByC(1-xy)Oz, where A, B, and C are one of Mn, Co, Mo, Ti, Al, Ni, and Nb, 0 < x < 1, 0 < y < 1. The lithium extraction active material is converted from the pre-delithiation active material.

[0037] The electron transport material can be Pt / C or Pd / C, which can catalyze both the reaction between hydrogen and the lithium-extraction active material, and the reaction between oxygen and the pre-delithiation active material. The electron transport material can also be a mixture of Co and Mn, with Mn acting during lithium extraction and Co acting during delithiation. The electron transport material is distributed in solution as particles or powder with a particle size of 20 nm-500 nm, while the active material (lithium-extraction active material / pre-delithiation active material) has a particle size of 100-500 μm.

[0038] Preferably, the oxidation peak of hydrogen oxidation is lower than the reaction peak of lithium ion insertion in the lithium-extraction active material, and the reduction peak of oxygen reduction is higher than the reaction peak of lithium ion removal in the pre-delithiation active material. More preferably, the electron transfer material (i.e., the catalyst) is a platinum-carbon catalyst, the lithium-extraction active material is iron phosphate, and the pre-delithiation active material is lithium iron phosphate. Figure 1 This is the CV curve of the oxidation reaction of hydrogen under platinum-carbon catalysis. It shows that the oxidation peak of hydrogen is at -0.84V. Figure 2 The reaction peak for the intercalation of lithium ions with iron phosphate is located at 0V, indicating that hydrogen oxidation can drive the lithium extraction reaction. Figure 3This is the CV curve of the reduction reaction of oxygen under platinum-carbon catalysis. The reduction peak is observed at 0.96 V. Figure 2 The reaction peak for lithium ion extraction from lithium iron phosphate was located at 0.33 V, indicating that oxygen reduction can drive the lithium extraction reaction.

[0039] The present invention will be further described below with reference to specific embodiments.

[0040] Example 1

[0041] Preparation of lithium-extracting active materials (pre-lithium-intercalated active materials):

[0042] 1. Take 15g of LiFePO4, add 150ml of water, and sonicate to disperse until the solution is homogeneous to obtain solution a;

[0043] 2. Take 22.5g of Na2S2O8, add 300ml of water, and stir well to obtain solution b;

[0044] 3. Add solution b to solution a and stir at 40°C for 5 hours. After the reaction is complete, filter the solution, place the solid in an oven and dry thoroughly to obtain the lithium-extraction active material FePO4. Grind it thoroughly into powder and collect it for later use.

[0045] Lithium extraction process: Using brine from a salt lake in Tibet as the lithium-containing solution and PT / C catalyst as the electron transfer medium, 15g of lithium extraction active material FePO4 and 750mg of PT / C catalyst were added to 1L of lithium-containing solution. Both were dispersed in the solution in particulate form. Then, 100% pure H2 was introduced into the lithium-containing solution at a gas flow rate of 100ml / min and the reaction was allowed to proceed for 2 hours. The reactions that occurred during the reaction were as follows:

[0046]

[0047] FePO4+Li + +e - →LiFePO4 Reaction Formula 2

[0048] Among them, reaction one is carried out under the action of pt / c catalyst.

[0049] The solution after the reaction was filtered to obtain filtrate 1. LiFePO4 with adsorbed lithium was obtained by filtration and collected for the next step of delithiation.

[0050] Delithiation process: Take the filtered LiFePO4 solid, add 100ml of water, and ultrasonically disperse it evenly. Then, introduce oxygen at a gas flow rate of 100ml / min to allow it to react fully for 2 hours. After the reaction, filter the solution to obtain filtrate 2. Place the filtered solid in an oven and dry it thoroughly to obtain the delithiated FePO4 solid.

[0051] The reactions that occur during delithiation are as follows:

[0052] LiFePO4→Li + +FePO4+e - Reaction 3

[0053]

[0054] Among them, reaction four is carried out under the action of pt / c catalyst.

[0055] ICP was used to measure the concentrations of different ions in the brine stock solution, filtrate 1, and filtrate 2, as shown in the table below. The lithium extraction rate was 92%, the lithium desorption rate was 95%, and the sodium ion retention rate was 96%. The brine stock solution was the initial ion concentration of the lithium-containing solution.

[0056] Brine stock solution (g / L) 0.49 73 0.03 17 0.15 Filtrate 1 (g / L) 0.04 70 0.03 16 0.13 Filtrate 2 (g / L) 4.1 15 0 0.5 0.2

[0057] Example 2

[0058] Preparation of lithium-extracting active materials (pre-lithium-intercalated active materials):

[0059] 1. Take 15g of LiFePO4, add 150ml of water, and sonicate to disperse until the solution is homogeneous to obtain solution a;

[0060] 2. Take 22.5g of Na2S2O8, add 300ml of water, and stir well to obtain solution b;

[0061] 3. Add solution b to solution a and stir at 40°C for 5 hours. After the reaction is complete, filter the solution, place the solid in an oven and dry thoroughly to obtain the lithium-extraction active material FePO4. Grind it thoroughly into powder and collect it for later use.

[0062] Lithium-extraction active material FePO4 coated with catalyst

[0063] 1. Take 750 mg pt / c and 200 μl Nafion solution, with the mass fraction of Nafion solution ωt% = 10%. Add the Nafion solution and catalyst pt / c to 30 ml of ethanol solution and disperse evenly by ultrasonication.

[0064] 2. Disperse the prepared ferric phosphate in 100ml of ethanol solution and mix it into a slurry. Then add the mixed solution of PT / C and Nafion to the ferric phosphate and mix well.

[0065] 3. Place the mixed slurry in a 60℃ oven to dry until the ethanol is completely evaporated. Grind the resulting solid into powder using a mortar and pestle to obtain the pre-lithium-intercalated active material with the catalyst coated on the surface of FePO4.

[0066] Lithium extraction process

[0067] Using brine from a salt lake in Tibet as a lithium-containing solution, 1 L of brine was added to the pre-lithiated active material coated on the surface of FePO4 with the catalyst prepared above. Then, 100% pure H2 was introduced at a gas flow rate of 10 ml / min and reacted for 5 h. The solution after reaction was filtered to obtain filtrate 1. The solid obtained by filtration was placed in an oven and dried thoroughly to obtain LiFePO4 solid after lithium extraction.

[0068] The following reactions occur during the process:

[0069]

[0070] FePO4+Li + +e - →LiFePO4 Reaction Formula 2

[0071] Among them, reaction one is carried out under the action of pt / c catalyst.

[0072] Delithiation process

[0073] Take the above-mentioned lithium-extracted LiFePO4 solid, add 100ml of water, and ultrasonically disperse it evenly. Then, introduce oxygen at a gas flow rate of 10ml / min to allow it to react fully for 5 hours. After the reaction, filter the solution to obtain filtrate 2. Place the solid in an oven and dry it thoroughly to obtain the separated FePO4 solid.

[0074] The reactions that occur during delithiation are as follows:

[0075] LiFePO4→Li + +FePO4+e - Reaction 3

[0076]

[0077] Among them, reaction four is carried out under the action of pt / c catalyst.

[0078] The concentrations of different ions in the brine stock solution (containing lithium), filtrate 1 and filtrate 2 were measured using ICP, as shown in the table below. The lithium extraction rate was 95%, the lithium desorption rate was 96%, and the sodium ion retention rate was 96%.

[0079] brine stock solution (g / L) 0.49 73 0.03 17 0.15 Filtrate 1 (g / L) 0.03 70 0.03 15 0.14 Filtrate 2 (g / L) 4.4 12 0 0.6 0.1

[0080] Example 3

[0081] Preparation of lithium-extracting active materials (pre-lithium-intercalated active materials):

[0082] 1. Take 15g of LiFePO4, add 150ml of water, and disperse by ultrasonication to obtain solution a uniformly;

[0083] 2. Take 22.5g of Na2S2O8, add 300ml of water, and stir until homogeneous to obtain solution b;

[0084] 3. Add solution b to solution a and stir at 40°C for 5 hours. After the reaction is complete, filter the solution, place the solid in an oven and dry thoroughly to obtain the lithium-extraction active material FePO4. Grind it thoroughly into powder and collect it for later use.

[0085] Lithium extraction process: Using brine from a salt lake in Tibet as the lithium-containing solution, and a mixed catalyst of MnO2 and CoO as the electron transfer medium, 15g of lithium extraction active material FePO4, 1g of MnO2, and 1g of CoO catalyst were added to 1L of the lithium-containing solution. Both the lithium extraction active material and the catalyst were dispersed in the solution as particles. Then, 100% pure H2 was introduced into the lithium-containing solution at a gas flow rate of 100ml / min, and the reaction was allowed to proceed for 2 hours. The reactions that occurred during the process are as follows:

[0086]

[0087] FePO4+Li + +e - →LiFePO4 Reaction Formula 2

[0088] Among them, reaction one is carried out under the action of MnO2 and CoO catalysts.

[0089] The solution after the reaction was filtered to obtain filtrate 1. LiFePO4 with adsorbed lithium was obtained by filtration and collected for the next step of delithiation.

[0090] Delithiation process: Take the filtered LiFePO4 solid, add 100ml of water, and ultrasonically disperse it evenly. Then, introduce oxygen at a gas flow rate of 100ml / min to allow it to react fully for 2 hours. After the reaction, filter the solution to obtain filtrate 2. Place the filtered solid in an oven and dry it thoroughly to obtain the delithiated FePO4 solid.

[0091] The reactions that occur during delithiation are as follows:

[0092] LiFePO4→Li + +FePO4+e - Reaction 3

[0093]

[0094] Among them, reaction four is carried out under the action of MnO2 and CoO catalysts.

[0095] The concentrations of different ions in the brine stock solution (containing lithium), filtrate 1, and filtrate 2 were measured using ICP, as shown in the table below. The lithium extraction rate was 90%, the lithium desorption rate was 91%, and the sodium ion retention rate was 90%.

[0096] Brine stock solution (g / L) 0.49 73 0.03 17 0.15 Filtrate 1 (g / L) 0.05 66 0.03 13 0.12 Filtrate 2 (g / L) 4.0 24 0 2 0.2

[0097] Example 4

[0098] Preparation of lithium-extracting active materials (pre-lithium-intercalated active materials):

[0099] 1. Take 15g of LiFePO4, add 150ml of water, and disperse by ultrasonication to obtain solution a uniformly;

[0100] 2. Take 22.5g of Na2S2O8, add 300ml of water, and stir until homogeneous to obtain solution b;

[0101] 3. Add solution b to solution a and stir at 40°C for 5 hours. After the reaction is complete, filter the solution, place the solid in an oven and dry thoroughly to obtain the lithium-extraction active material FePO4. Grind it thoroughly into powder and collect it for later use.

[0102] Lithium extraction process: Using brine from a salt lake in Tibet as the lithium-containing solution, and NiO and Co3O4 as electron transfer catalysts, 15g of lithium extraction active material FePO4, 1.2g of NiO catalyst, and 1.2g of N Co3O4 catalyst were added to 1L of the lithium-containing solution. The lithium extraction active material and catalysts were dispersed in the solution. Then, 100% pure H2 was introduced into the lithium-containing solution at a gas flow rate of 50ml / min, and the reaction was allowed to proceed for 2 hours. The reactions that occurred during the reaction are as follows:

[0103]

[0104] FePO4+Li + +e - →LiFePO4 Reaction Formula 2

[0105] Among them, reaction one is carried out under the action of NiO and Co3O4 catalysts.

[0106] The solution after the reaction was filtered to obtain filtrate 1. LiFePO4 with adsorbed lithium was obtained by filtration and collected for the next step of delithiation.

[0107] Delithiation process: Take the filtered LiFePO4 solid, add 100ml of water, ultrasonically disperse it evenly, and then pass oxygen at a gas flow rate of 50ml / min to allow it to react fully for 2 hours. After the reaction, filter the solution to obtain filtrate 2. Place the filtered solid in an oven and dry it thoroughly to obtain the delithiated FePO4 solid.

[0108] The reactions that occur during delithiation are as follows:

[0109] LiFePO4→Li + +FePO4+e - Reaction 3

[0110]

[0111] Among them, reaction four is carried out under the action of NiO and Co3O catalysts.

[0112] ICP was used to measure the concentrations of different ions in the brine stock solution, filtrate 1, and filtrate 2, as shown in the table below. The lithium extraction rate was 93%, the lithium desorption rate was 94%, and the sodium ion retention rate was 96%. The brine stock solution was the initial ion concentration of the lithium-containing solution.

[0113] brine stock solution (g / L) 0.49 73 0.03 17 0.15 Filtrate 1 (g / L) 0.03 71 0.03 16 0.13 Filtrate 2 (g / L) 4.2 13 0 0.2 0.2

[0114] Example 5

[0115] Preparation of lithium-extracting active materials (pre-lithium-intercalated active materials):

[0116] 1. Take 15g of LiCoO2, add 150ml of water, and disperse by ultrasonication to obtain solution a uniformly;

[0117] 2. Take 16.4g of Na2S2O8, add 250ml of water, and stir until homogeneous to obtain solution b;

[0118] 3. Add solution b to solution a and stir at 40°C for 5 hours. After the reaction is complete, filter the solution, place the solid in an oven and dry thoroughly to obtain the lithium-extraction active material CoO2. Grind it thoroughly into powder and collect it for later use.

[0119] Lithium extraction process: Using brine from a salt lake in Tibet as the lithium-containing solution and PT / C catalyst as the electron transfer medium, 15g of lithium extraction active material CoO2 and 750mg of PT / C catalyst were added to 1L of lithium-containing solution. Both were dispersed in the solution in particulate form. Then, 100% pure H2 was introduced into the lithium-containing solution at a gas flow rate of 100ml / min and the reaction was allowed to proceed for 2 hours. The reactions that occurred during the reaction were as follows:

[0120]

[0121] CoO2+Li + +e - →LiCoO2 Reaction Formula 2

[0122] Among them, reaction one is carried out under the action of pt / c catalyst.

[0123] The solution after the reaction was filtered to obtain filtrate 1. LiCoO2 with adsorbed lithium was obtained by filtration and collected for the next step of delithiation.

[0124] Delithiation process: Take the filtered LiCoO2 solid, add 100ml of water, ultrasonically disperse it evenly, and then pass oxygen at a gas flow rate of 100ml / min to allow it to react fully for 2 hours. After the reaction, filter the solution to obtain filtrate 2. Place the filtered solid in an oven and dry it thoroughly to obtain delithiated CoO2 solid.

[0125] The reactions that occur during delithiation are as follows:

[0126] LiCoO2→Li + +CoO2+e - Reaction 3

[0127]

[0128] Among them, reaction four is carried out under the action of pt / c catalyst.

[0129] ICP was used to measure the concentrations of different ions in the brine stock solution, filtrate 1, and filtrate 2, as shown in the table below. The lithium extraction rate was 89%, the lithium desorption rate was 90%, and the sodium ion retention rate was 98%. The brine stock solution was the initial ion concentration of the lithium-containing solution.

[0130] brine stock solution (g / L) 0.49 73 0.03 17 0.15 Filtrate 1 (g / L) 0.05 72 0.03 15 0.14 Filtrate 2 (g / L) 4.1 9 0 0.5 0.1

[0131] Comparative Example 1

[0132] Similar to Example 1, the difference is that hydrogen gas was not introduced during the lithium extraction process, while the other operation steps are the same.

[0133] The concentrations of different ions in the filtrate were measured using ICP, as shown in the table below. The lithium extraction rate was 0.

[0134] Brine stock solution (g / L) 0.49 73 0.03 17 0.15 Filtrate 1 (g / L) 0.49 72 0.03 17 0.15 Filtrate 2 (g / L) 0 0 0 0 0

[0135] This indicates that without hydrogen participating in the catalytic reaction, the lithium extraction reaction will not be driven.

[0136] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for extracting and enriching lithium from a lithium-containing solution, characterized in that, Includes the following steps Lithium extraction: Using hydrogen as a reducing agent, electrons are transferred from hydrogen to a lithium extraction active material using a Pt / C catalyst, a Pd / C catalyst, a mixed catalyst of MnO2 and CoO, or a mixed catalyst of NiO and Co3O4. The lithium extraction active material adsorbs lithium ions in a lithium-containing solution to obtain a pre-delithiation active material. Delithiation: Using oxygen as the oxidant, electrons are transferred from the pre-delithiation active material to oxygen using a Pt / C catalyst, a Pd / C catalyst, a mixed catalyst of MnO2 and CoO, or a mixed catalyst of NiO and Co3O4. The pre-delithiation active material releases lithium ions into the lithium extraction solution.

2. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, The pre-delithiation active material is at least one of lithium iron phosphate, lithium manganese oxide, and ternary metal composite oxides; wherein the lithium iron phosphate is one or a mixture of several of LiFePO4, LixMeyFePO4, LiFexMeyPO4, LiFePO4 / C, LixMeyFePO4 / C, and LiFexMeyPO4 / C, wherein Me is one or a mixture of several of Mn, Co, Mo, Ti, Al, Ni, and Nb, 0 < x < 1, 0 < y < 1; the lithium manganese oxide is LiMn2O4, LiMnO2, LixMeyMnO2, or LiMn x Me y PO4, LiMnO2 / C, Li x Me y MnO2 / C, LiMn x Me y The ternary metal composite oxide is a mixture of one or more of the following: O2 / C, wherein Me is a mixture of one or more of Co, Mo, Ti, Al, Ni, and Nb, 0 < x < 1, 0 < y < 1; the ternary metal composite oxide is LiA. x B y C (1-x-y) O z Where A, B, and C are one or more of Mn, Co, Mo, Ti, Al, Ni, and Nb, and 0 < x < 1, 0 < y < 1.

3. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, The catalysts used in lithium extraction and delithiation processes may be the same or different.

4. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, The catalyst and the lithium extraction active material are separate; The catalyst is dispersed in the lithium extraction solution or lithium-containing solution as particulates; The lithium extraction active material is dispersed in particulate form in the lithium-containing solution; The pre-delithiation active material is dispersed in the lithium extraction solution as particles.

5. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, The catalyst is attached to the surface of the lithium extraction active material or the pre-delithiation active material; the lithium extraction active material or the pre-delithiation active material is dispersed in the corresponding solution as particles.

6. The method for extracting and enriching lithium from a lithium-containing solution according to claim 5, characterized in that, The method for preparing catalysts by attaching them to the surface of lithium-extraction active materials or pre-delithiation active materials is as follows: First, the catalyst and Nafion solution are added to the ethanol solution to allow the Nafion and catalyst to come into full contact and form a mixed solution. Add the pre-delithiation active material or the lithium extraction active material to the mixed solution and grind it thoroughly to obtain a well mixed slurry; The solid is dried until the ethanol has completely evaporated, and then ground into powder using a mortar and pestle to obtain a catalyst-coated lithium extraction active material or a pre-delithiation active material.

7. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, After lithium extraction is completed, the active lithium extraction material and catalyst in the lithium-containing solution are obtained and placed in the lithium extraction solution, and oxygen is introduced to remove lithium.

8. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, The process of using a catalyst to transfer electrons from hydrogen to lithium-extraction active material can be a single-stage reaction or a multi-stage reaction. In the case of a single-stage reaction, the catalyst directly transfers electrons from hydrogen to the lithium-extraction active material. In the case of a multi-stage reaction, the catalyst includes a first catalyst and a second catalyst, and the electrons from hydrogen are transferred to the lithium-extraction active material sequentially through the first catalyst and the second catalyst. The process of transferring electrons from a pre-delithiated active material to oxygen using a catalyst can be a single-stage or multi-stage reaction. In a single-stage reaction, the catalyst directly transfers electrons from hydrogen to the pre-delithiated active material. In a multi-stage reaction, the catalyst includes a first catalyst and a second catalyst, and electrons from oxygen are transferred to the pre-delithiated active material sequentially through the first catalyst and the second catalyst.

9. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1, characterized in that, The mass ratio of the catalyst to the lithium extraction active material or the pre-delithiation active material is (2~20):

100.

10. The method for extracting and enriching lithium from a lithium-containing solution according to claim 1 or 9, characterized in that, The mass ratio of the catalyst to the lithium extraction active material or the pre-delithiation active material is (5~10):100.

Images