Method for selectively leaching lithium in waste lithium iron phosphate electrode material

Abstract

The invention relates to the technical field of resource recycling, and particularly discloses a method for selectively leaching lithium in a waste lithium iron phosphate electrode material. According to the method, oxygen or air is used as an oxidizing agent, nitrilotriacetic acid is used as a leaching agent, and lithium is selectively leached from the waste lithium iron phosphate electrode material by adopting a wet leaching process. The oxidizing agent used in the method is air or oxygen which is cheap and easy to obtain; according to the method, the leaching condition is mild, the leaching speed is high, and the leaching efficiency is high; the nitrilotriacetic acid leaching agent used in the method can be regenerated and recycled through a simple method, and the reagent cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recycling, and in particular to a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. Background Art

[0002] Waste lithium iron phosphate batteries are rich in the metallic element lithium, with lithium content generally exceeding that of primary ore grades, making them extremely valuable for recycling. Recycling and reusing these batteries offers significant economic and environmental benefits. Recycling these batteries not only alleviates the environmental pressures posed by battery waste but also ensures the security and stability of my country's critical lithium metal supply chain, contributing to the green and sustainable development of the new energy industry.

[0003] Compared to discarded lithium cobalt oxide or ternary lithium batteries, the recycling of discarded lithium iron phosphate batteries offers lower added value and is more sensitive to recycling costs due to the absence of high-value metals such as cobalt and nickel. The lithium iron phosphate cathode material (LiFePO4) is the most valuable component of discarded lithium iron phosphate batteries and is typically recovered using a wet leaching process. Existing leaching processes are primarily divided into full leaching of valuable elements and selective lithium leaching. Full leaching typically uses a large amount of acid to simultaneously leach elements such as Li and Fe from the lithium iron phosphate material into a solution. The Fe in the leachate is then precipitated as hydroxide or phosphate by adjusting the pH and adding oxidants, achieving separation of Li and Fe. Because full leaching requires the simultaneous dissolution of Li and Fe, followed by subsequent separate precipitation, the consumption of acid and alkali reagents is high, making it less economical. Selective lithium leaching typically employs oxidative leaching, using inorganic or organic acids in combination with oxidants such as hydrogen peroxide to selectively leach Li from the lithium iron phosphate material, while Fe is primarily precipitated in the slag as FePO4. Compared with the full leaching process, the selective lithium leaching process only needs to dissolve Li, so the consumption of leaching agent is greatly reduced and the economy is improved.

[0004] In existing selective lithium leaching processes, hydrogen peroxide is often used as an oxidant. However, in actual use, hydrogen peroxide has been found to have problems such as easy decomposition, low utilization rate, and high price. Currently, there are reports of selective lithium leaching from waste lithium iron phosphate materials using oxygen as an oxidant and inorganic acids such as sulfuric acid as leaching agents. However, there are problems such as low leaching efficiency and demanding reaction conditions. For example, the leaching reaction needs to be carried out at relatively high temperatures (96-150°C) and pressures (0.2-1.9MPa), which places high demands on equipment and increases the investment and processing costs of recycling.

[0005] Therefore, in order to solve the above problems, it is necessary to develop a method for selectively leaching lithium from waste lithium iron phosphate electrode materials with good leaching effect and low processing cost. Summary of the Invention

[0006] The main technical problem solved by the present invention is to provide a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method of the present invention has good leaching effect and low processing cost.

[0007] To solve the above technical problems, the present invention adopts a technical solution: a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method uses oxygen or air as an oxidant and nitrilotriacetic acid as a leaching agent to selectively leach lithium from waste lithium iron phosphate electrode materials using a wet leaching process. Nitrilotriacetic acid is nitrilotriacetic acid, also known as aminotriacetic acid.

[0008] As an embodiment of the present invention, the method for selectively leaching lithium from waste lithium iron phosphate electrode materials includes the steps of: placing waste lithium iron phosphate electrode materials, water, and nitrotriacetic acid into a leaching reactor to obtain a leaching reaction system, introducing air or oxygen into the leaching reaction system to carry out a selective leaching reaction of lithium, and separating the solid and liquid after the reaction is completed to obtain a lithium leaching solution and lithium leaching residue.

[0009] In one embodiment of the present invention, the lithium salt is recovered from the lithium immersion solution by precipitation, and solid-liquid separation is performed to obtain a lithium salt solid, and the obtained liquid phase is the lithium precipitate solution. The lithium salt can be recovered from the lithium immersion solution by precipitation using conventional methods, such as adding sodium carbonate to react to obtain a lithium carbonate precipitate. This invention is not limited to this.

[0010] As one embodiment of the present invention, sulfuric acid is added to the lithium precipitation solution to react and precipitate nitrilotriacetic acid, which is then regenerated by solid-liquid separation. The regenerated nitrilotriacetic acid can be reused as a leaching agent.

[0011] As an embodiment of the present invention, the waste lithium iron phosphate electrode material is electrode powder obtained by disassembling and sorting waste lithium iron phosphate batteries.

[0012] As an embodiment of the present invention, the molar number of Li in the waste lithium iron phosphate electrode material is equal to the molar number of H in the nitrotriacetic acid. + The molar ratio is (0.93~1.10):1.

[0013] As an embodiment of the present invention, the solid-liquid ratio of the leaching reaction system is 100 to 500 g / L.

[0014] As an embodiment of the present invention, the leaching reaction is carried out under normal pressure and the reaction temperature is 25-60°C.

[0015] As an embodiment of the present invention, the reaction time of the leaching reaction is 30 to 120 minutes.

[0016] As an embodiment of the present invention, sulfuric acid is added to maintain the pH value of the reaction solution at 0.5 to 2.5 during the reaction.

[0017] As an embodiment of the present invention, after sulfuric acid is added to the lithium precipitation solution, the reaction is carried out for 30 to 120 minutes to precipitate nitrilotriacetic acid.

[0018] The present invention provides a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method uses nitrotriacetic acid as a leaching agent and air or oxygen as an oxidant to selectively leach lithium from waste lithium iron phosphate electrode materials. After the selective lithium leaching reaction is completed, lithium is enriched in the lithium leaching solution, while impurity elements such as iron are enriched in the lithium leaching residue. The lithium leaching solution is then used to recover lithium salts through precipitation, yielding a lithium precipitation solution rich in nitrotriacetic acid salts. By adding an appropriate amount of sulfuric acid to the lithium precipitation solution and adjusting the pH of the solution, nitrotriacetic acid can be precipitated from the solution. The nitrotriacetic acid is recovered through solid-liquid separation and reused in the selective lithium leaching process, thereby achieving a regeneration cycle of the nitrotriacetic acid and reducing reagent costs.

[0019] The present invention uses nitrilotriacetic acid as a leaching agent and air or oxygen as an oxidant, enabling efficient and preferential lithium leaching under mild conditions. The nitrilotriacetic acid consumed during the lithium leaching process can be regenerated after lithium recovery and returned to the selective lithium leaching process. Furthermore, the lithium leaching process of the present invention does not use hydrogen peroxide, which is easily decomposed and relatively expensive, thereby reducing the cost of the oxidant reagent in the recovery process. The nitrilotriacetic acid consumed during the lithium leaching process can be regenerated and recycled, further reducing costs.

[0020] The oxidant used in the method of the present invention is air or oxygen, which is inexpensive and readily available, and does not cause decomposition and waste. The method of the present invention also provides mild leaching conditions, a fast leaching rate, and high leaching efficiency. The nitrilotriacetic acid leaching agent used in the method of the present invention can be regenerated and reused through a simple method, reducing reagent costs. Therefore, the method provided by the present invention for selectively leaching lithium from waste lithium iron phosphate electrode materials using nitrilotriacetic acid and air / oxygen will be an important technical direction for the future recovery of waste lithium iron phosphate batteries and has great potential for industrial application. DETAILED DESCRIPTION

[0021] The following examples are intended to further illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0022] In the following examples and comparative examples, unless otherwise specified, the drugs used are all commercially available products.

[0023] Example 1

[0024] This embodiment provides a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method uses oxygen or air as an oxidant and nitrilotriacetic acid as a leaching agent to selectively leach lithium from waste lithium iron phosphate electrode materials using a wet leaching process.

[0025] The waste lithium iron phosphate electrode material to be processed is the electrode powder obtained by dismantling and sorting waste lithium iron phosphate batteries. The main components thereof are, by mass percentage, 3.87% lithium and 29.78% iron. The method specifically comprises the following steps:

[0026] (1) Putting waste lithium iron phosphate electrode material, water and nitrotriacetic acid into a leaching reactor, stirring and mixing to obtain a leaching reaction system, wherein: the molar number of Li in the waste lithium iron phosphate electrode material and the molar number of H in the nitrotriacetic acid are + The molar ratio of is 1.0:1, and the solid-liquid ratio of the leaching reaction system is 100g / L;

[0027] Air is continuously introduced into the leaching reaction system while stirring to carry out a selective leaching reaction of lithium. The leaching reaction is carried out under normal pressure, at a reaction temperature of 30° C., for a reaction time of 60 minutes. After the reaction is completed, the leaching solution and the leaching residue are separated by filtration to obtain a lithium leaching solution;

[0028] (2) adding sodium carbonate solution to the lithium immersion solution to react and generate lithium carbonate precipitate, and performing solid-liquid separation to obtain lithium carbonate solid, and the obtained liquid phase is the lithium precipitation solution;

[0029] (3) adding sulfuric acid to the lithium precipitation solution to adjust the pH value of the lithium precipitation solution to 1.0, stirring the reaction, and adding sulfuric acid during the reaction to keep the pH value of the reaction solution at about 1.0, and nitrotriacetic acid precipitates are precipitated by the reaction. The reaction is stopped after 60 minutes, and then the regenerated nitrotriacetic acid solid is obtained by solid-liquid separation.

[0030] The experimental results show that the leaching rate of lithium in step (1) is 94.87%, and the leaching rate of iron is 0.11%.

[0031] Example 2

[0032] This embodiment provides a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method uses oxygen or air as an oxidant and nitrilotriacetic acid as a leaching agent to selectively leach lithium from waste lithium iron phosphate electrode materials using a wet leaching process.

[0033] The waste lithium iron phosphate electrode material to be processed is the electrode powder obtained by dismantling and sorting waste lithium iron phosphate batteries. The main components thereof are, by mass percentage, 3.87% lithium and 29.78% iron. The method specifically comprises the following steps:

[0034] (1) Putting waste lithium iron phosphate electrode material, water and nitrotriacetic acid into a leaching reactor, stirring and mixing to obtain a leaching reaction system, wherein: the molar number of Li in the waste lithium iron phosphate electrode material and the molar number of H in the nitrotriacetic acid are + The molar ratio of is 0.93:1, and the solid-liquid ratio of the leaching reaction system is 300 g / L;

[0035] Air is continuously introduced into the leaching reaction system while stirring to carry out a selective leaching reaction of lithium. The leaching reaction is carried out under normal pressure, at a reaction temperature of 50° C., for a reaction time of 90 minutes. After the reaction is completed, the leaching solution and the leaching residue are separated by filtration to obtain;

[0036] (2) adding sodium carbonate solution to the lithium immersion solution to react and generate lithium carbonate precipitate, and performing solid-liquid separation to obtain lithium carbonate solid, and the obtained liquid phase is the lithium precipitation solution;

[0037] (3) Sulfuric acid was added to the lithium precipitation solution to adjust the pH value of the lithium precipitation solution to 1.5, and the reaction was stirred. During the reaction, the pH value of the reaction solution was maintained at about 1.5 by adding sulfuric acid, and nitrotriacetic acid precipitated. The reaction was stopped after 90 minutes, and then the regenerated nitrotriacetic acid solid was obtained by solid-liquid separation.

[0038] The experimental results show that the leaching rate of lithium in step (1) is 98.63%, and the leaching rate of iron is 5.28%.

[0039] Example 3

[0040] This embodiment provides a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method uses oxygen or air as an oxidant and nitrilotriacetic acid as a leaching agent to selectively leach lithium from waste lithium iron phosphate electrode materials using a wet leaching process.

[0041] The waste lithium iron phosphate electrode material to be processed is the electrode powder obtained by dismantling and sorting waste lithium iron phosphate batteries, and its main components are as follows by mass percentage: 2.34% lithium and 14.16% iron. The method specifically includes the following steps:

[0042] (1) Putting waste lithium iron phosphate electrode material, water and nitrotriacetic acid into a leaching reactor, stirring and mixing to obtain a leaching reaction system, wherein: the molar number of Li in the waste lithium iron phosphate electrode material and the molar number of H in the nitrotriacetic acid are + The molar ratio of 1:1 is 1.10:1, and the solid-liquid ratio of the leaching reaction system is 500 g / L;

[0043] The leaching reaction system is continuously introduced with oxygen and stirred to carry out a selective leaching reaction of lithium. The leaching reaction is carried out under normal pressure, at a reaction temperature of 60° C., for a reaction time of 120 minutes. After the reaction is completed, the leaching solution and the leaching residue are obtained by filtration and separation.

[0044] (2) adding sodium carbonate solution to the lithium immersion solution to react and generate lithium carbonate precipitate, and performing solid-liquid separation to obtain lithium carbonate solid, and the obtained liquid phase is the lithium precipitation solution;

[0045] (3) Sulfuric acid was added to the lithium precipitation solution to adjust the pH value of the lithium precipitation solution to 0.5, and the reaction was stirred. During the reaction, the pH value of the reaction solution was maintained at about 0.5 by adding sulfuric acid. Nitrilotriacetic acid precipitate was precipitated by the reaction. The reaction was stopped after 30 minutes, and then the regenerated nitrilotriacetic acid solid was obtained by solid-liquid separation.

[0046] The experimental results show that the leaching rate of lithium in step (1) is 96.09%, and the leaching rate of iron is 0%.

[0047] Example 4

[0048] This embodiment provides a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The method uses oxygen or air as an oxidant and nitrilotriacetic acid as a leaching agent to selectively leach lithium from waste lithium iron phosphate electrode materials using a wet leaching process.

[0049] The waste lithium iron phosphate electrode material to be processed is the electrode powder obtained by dismantling and sorting waste lithium iron phosphate batteries. The main components thereof are, by mass percentage, 3.87% lithium and 29.78% iron. The method specifically comprises the following steps:

[0050] (1) Putting waste lithium iron phosphate electrode material, water and nitrotriacetic acid into a leaching reactor, stirring and mixing to obtain a leaching reaction system, wherein: the molar number of Li in the waste lithium iron phosphate electrode material and the molar number of H in the nitrotriacetic acid are + The molar ratio of is 1.0:1, and the solid-liquid ratio of the leaching reaction system is 200g / L;

[0051] The leaching reaction system is continuously introduced with oxygen and stirred to carry out a selective leaching reaction of lithium. The leaching reaction is carried out under normal pressure, at a reaction temperature of 60° C., for a reaction time of 30 minutes. After the reaction is completed, the leaching solution and the leaching residue are separated by filtration to obtain a lithium leaching solution.

[0052] (2) adding sodium carbonate solution to the lithium immersion solution to react and generate lithium carbonate precipitate, and performing solid-liquid separation to obtain lithium carbonate solid, and the obtained liquid phase is the lithium precipitation solution;

[0053] (3) Sulfuric acid was added to the lithium precipitation solution to adjust the pH value of the lithium precipitation solution to 2.0, and the reaction was stirred. During the reaction, the pH value of the reaction solution was maintained at about 2.0 by adding sulfuric acid. Nitrilotriacetic acid precipitate was precipitated by the reaction. The reaction was stopped after 120 minutes, and then the regenerated nitrilotriacetic acid solid was obtained by solid-liquid separation.

[0054] The experimental results show that the leaching rate of lithium in step (1) is 94.02%, and the leaching rate of iron is 0.02%.

[0055] Comparative Example

[0056] This comparative example provides a method for selectively leaching lithium from waste lithium iron phosphate electrode materials. The waste lithium iron phosphate electrode materials to be treated are electrode powders obtained by disassembling and sorting waste lithium iron phosphate batteries. The main components of the electrode powders are, by mass percentage, 3.87% lithium and 29.78% iron. The method specifically comprises the following steps:

[0057] The waste lithium iron phosphate electrode material, water and sulfuric acid are placed in a leaching reactor and stirred to obtain a leaching reaction system, wherein: the molar number of Li in the waste lithium iron phosphate electrode material is equal to the molar number of H in the sulfuric acid. + The molar ratio of is 1.0:1, and the solid-liquid ratio of the leaching reaction system is 100g / L;

[0058] Air is continuously introduced into the leaching reaction system while stirring to carry out a selective leaching reaction of lithium. The leaching reaction is carried out under normal pressure, at a reaction temperature of 30° C., for 60 minutes. After the reaction is completed, the solution is filtered and separated to obtain a lithium leaching solution and a lithium leaching residue.

[0059] The experimental results showed that the leaching rate of lithium was 55.61% and the leaching rate of iron was 23.43%.

[0060] Compared with Example 1, sulfuric acid was used instead of nitrotriacetic acid in the comparative example. The comparison showed that the use of the nitrotriacetic acid-air system could achieve the effect of efficient and selective lithium leaching.

[0061] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or any direct or indirect application in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for selectively leaching lithium from waste lithium iron phosphate electrode materials, characterized in that: The method uses oxygen or air as an oxidant and nitrilotriacetic acid as a leaching agent, and adopts a wet leaching process to selectively leach lithium from waste lithium iron phosphate electrode materials.

2. The method according to claim 1, characterized in that The method comprises the following steps: placing waste lithium iron phosphate electrode materials, water and nitrotriacetic acid into a leaching reactor to obtain a leaching reaction system; introducing air or oxygen into the leaching reaction system to perform a selective leaching reaction of lithium; and performing solid-liquid separation after the reaction is completed to obtain a lithium leaching solution and lithium leaching residue.

3. The method according to claim 2, characterized in that The lithium leaching solution is used to recover lithium salts by precipitation method, and solid-liquid separation is performed to obtain lithium salt solids, and the obtained liquid phase is the lithium precipitation solution.

4. The method according to claim 3, characterized in that Sulfuric acid is added into the lithium precipitation solution to react, nitrotriacetic acid precipitates are precipitated, and regenerated nitrotriacetic acid is obtained through solid-liquid separation.

5. The method according to claim 1 or 2, characterized in that The waste lithium iron phosphate electrode material is electrode powder obtained by disassembling and sorting waste lithium iron phosphate batteries.

6. The method according to claim 2, characterized in that The molar number of Li in the waste lithium iron phosphate electrode material and the molar number of H in the nitrotriacetic acid + The molar ratio is (0.93~1.10):

1.

7. The method according to claim 2, characterized in that The solid-liquid ratio of the leaching reaction system is 100-500 g / L.

8. The method according to claim 7, characterized in that The leaching reaction is carried out under normal pressure at a reaction temperature of 25 to 60° C.; and / or the reaction time of the leaching reaction is 30 to 120 minutes.

9. The method according to claim 4, characterized in that Sulfuric acid is added to maintain the pH value of the reaction solution at 0.5 to 2.5 during the reaction.

10. The method according to claim 4, characterized in that The reaction time is 30 to 120 minutes.