Method for recovering iron phosphate from waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag and application

Abstract

The invention provides a method for recycling iron phosphate from waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag and application of the method. The method comprises the steps that 1, the waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag and hydrochloric acid are placed in a reaction kettle to leach out metal elements in the slag, and filtering is conducted to obtain filtrate and graphite slag; step 2, detecting the contents of copper ions and aluminum ions in the filtrate, calculating the amount of required iron powder, adding the iron powder into the filtrate to remove the copper ions in the filtrate, adjusting the pH value to remove the aluminum ions, and oxidizing ferrous iron in the filtrate into ferric iron by using an oxidizing agent; 3, ammonia water and ammonium dihydrogen phosphate are added into the filtrate, the ammonia water is used for adjusting the PH, the ammonium dihydrogen phosphate is used for adjusting the iron-phosphorus ratio to be 0.96-1.02, an iron phosphate dihydrate precipitate is synthesized through a synthesis reaction, and iron phosphate dihydrate and lithium-containing filtrate are obtained through solid-liquid separation; and 4, washing and drying the iron phosphate dihydrate precipitate to obtain regenerated iron phosphate. The economic benefit of recycling the waste lithium iron phosphate battery is increased, and the generation of solid wastes is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery recycling, and specifically relates to a method and application of recycling iron phosphate from mixed lithium extraction slag from waste lithium iron phosphate positive and negative electrodes. Background Art

[0002] Lithium iron phosphate batteries have been widely used in electric vehicles and energy storage due to their good cycle stability and safety. However, the limited service life of lithium-ion batteries has led to the retirement of a large number of lithium iron phosphate batteries. The industrial recycling of lithium iron phosphate batteries mainly involves dismantling and crushing the batteries, powdering and sorting, obtaining waste lithium iron phosphate positive and negative electrode mixtures, and extracting lithium from the waste lithium iron phosphate positive and negative electrode mixtures. After lithium extraction, the lithium extraction slag contains a large amount of iron phosphate, graphite slag and a small amount of copper, aluminum and lithium elements. Most companies do not attach importance to the recycling value of lithium extraction slag and dispose of lithium extraction slag as solid waste, resulting in waste of resources and environmental impact. In view of the problem of insufficient utilization of lithium extraction slag in the existing waste lithium iron phosphate positive and negative electrode mixed powder hydrometallurgical recovery process, it is necessary to develop a method for recycling lithium extraction slag from waste lithium iron phosphate battery positive and negative electrode mixtures. Summary of the invention

[0003] The purpose of the present invention is to provide a method and application of recovering iron phosphate from mixed lithium extraction slag of waste lithium iron phosphate positive and negative electrodes. The method separates graphite slag and iron phosphate slag by hydrochloric acid leaching. The graphite slag can be used as refractory materials after treatment. The iron phosphate slag is subjected to iron powder impurity removal, oxidation, ammonia water and diammonium phosphate synthesis to obtain regenerated iron phosphate. The small amount of lithium in the lithium extraction slag can be reused in the lithium extraction process by concentration. Recycling the lithium extraction slag increases the economic benefits of recycling waste lithium iron phosphate batteries and reduces the generation of solid waste. The specific scheme is as follows:

[0004] According to the first aspect of the present invention, one or more embodiments of the present application provide a method for recovering iron phosphate from waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag, which comprises:

[0005] Step 1, placing the waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag and hydrochloric acid in a reactor to leach the metal elements therein, and filtering to obtain a filtrate and graphite slag;

[0006] Step 2: Detect the content of copper ions and aluminum ions in the filtrate, calculate the required amount of iron powder, add iron powder to the filtrate to remove the copper ions and aluminum ions in the filtrate, adjust the pH to remove the aluminum ions, and then use an oxidant to oxidize the divalent iron in the filtrate to trivalent iron;

[0007] Step 3, adding ammonia water and diammonium phosphate to the filtrate, wherein the ammonia water is used to adjust the pH, and the diammonium phosphate is used to adjust the iron-phosphorus ratio to 0.96-1.02, synthesizing dihydrate iron phosphate precipitate through a synthesis reaction, and performing solid-liquid separation to obtain dihydrate iron phosphate and a lithium-containing filtrate;

[0008] Step 4: The ferric phosphate dihydrate precipitate is washed and dried to become regenerated ferric phosphate.

[0009] According to the above technical solution of the present invention, the following improvements can also be made:

[0010] The concentration of the hydrochloric acid is 25-40%, and the actual usage of the hydrochloric acid is 1-1.4 times of the theoretical usage.

[0011] Wherein, the reaction temperature of the hydrochloric acid leaching is 40-80°C, and the reaction time is 1-4h.

[0012] Wherein, the oxidant is at least one of oxygen, hydrogen peroxide and chlorine.

[0013] Wherein, the oxidation time is 10 to 30 minutes, and the oxidation temperature is 40 to 80°C.

[0014] Wherein, the temperature of the synthesis reaction is 40-100° C., and the time of the synthesis reaction is 30-90 minutes.

[0015] Wherein, the pH of the synthesis reaction is 1-3.

[0016] Wherein, the concentration of the diammonium phosphate is 1.2-2 mol / L.

[0017] According to the second aspect of the present invention, one or more embodiments in the present application provide an application of a method for recovering iron phosphate from mixed lithium extraction slag from waste lithium iron phosphate positive and negative electrodes, characterized in that the graphite slag obtained in step one is used as a refractory material after washing and drying, and the lithium-containing filtrate obtained in step three is concentrated and used to extract the lithium element.

[0018] According to the third aspect of the present invention, one or more embodiments of the present application provide an application of a method for recovering iron phosphate from waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag, and the method for recovering iron phosphate from waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag described in any one of the above is used to recover valuable elements from waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag. .

[0019] The beneficial effects of the present invention are:

[0020] Compared with the prior art, the present invention provides a method and application for recovering iron phosphate from lithium extraction residues of waste lithium iron phosphate positive and negative electrode mixtures. The embodiment of the present application uses hydrochloric acid to leach metal ions in the lithium extraction residues of waste lithium iron phosphate positive and negative electrode mixtures to separate graphite residues from valuable metal elements. Iron phosphate dihydrate is formed by oxidation and synthetic precipitation, and the iron phosphate dihydrate is washed and dried to become regenerated iron phosphate. The lithium element remaining in the lithium extraction residue is concentrated by solution and reused in the lithium extraction process. Based on the problem of waste resources and environmental pollution of lithium extraction residues of waste lithium iron phosphate positive and negative electrode mixtures, the embodiment of the present application proposes a method for recovering iron phosphate from lithium extraction residues of waste lithium iron phosphate positive and negative electrode mixtures, which effectively recycles and utilizes lithium extraction residues of waste lithium iron phosphate positive and negative electrode mixtures, and provides a new method for the problem of industrial treatment of lithium extraction residues of waste lithium iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention provides a flow chart of a method for recovering iron phosphate from mixed lithium extraction slag of waste lithium iron phosphate positive and negative electrodes. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0023] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present application should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in one or more embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "include" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] As attached Figure 1 As shown, this embodiment provides a method and application for recovering iron phosphate from mixed lithium phosphate slag from waste lithium iron phosphate positive and negative electrodes, and the method comprises the following steps:

[0025] (1) The lithium slag extracted from the waste lithium iron phosphate positive and negative electrode mixture is mixed with an appropriate amount of hydrochloric acid and then placed in a reactor. The reactor is heated in a vacuum drying oven to react and the metal elements in the lithium slag are leached. The filtrate and graphite slag are filtered through a circulating water vacuum filtration pump to obtain the filtrate and the graphite slag. The graphite slag can be used as a refractory material after multiple washing and drying;

[0026] (2) testing the copper ion and aluminum ion contents of the filtrate obtained in step (1), calculating the amount of iron powder required, adding an appropriate amount of iron powder to the filtrate obtained in step (1) to remove impurities, and determining the reaction stop condition by an online copper ion detector and an online aluminum ion detector. When the copper ion content is lower than 10 ppm, a sodium hydroxide solution is used to adjust the pH to generate aluminum hydroxide precipitation; when the aluminum ion content is lower than 50 ppm, the reaction is terminated, and the copper slag and aluminum slag are removed by solid-liquid separation to obtain an iron-rich liquid;

[0027] (3) introducing an oxidant into the iron-rich liquid obtained in step (2) to oxidize the divalent iron in the filtrate into trivalent iron, and convert the ferrous chloride into ferric chloride;

[0028] (4) adding an appropriate amount of ammonium dihydrogen phosphate to the filtrate obtained in step (3) to adjust the phosphorus-iron ratio, and adjusting the pH with ammonia water to synthesize ferric phosphate dihydrate precipitate, and performing solid-liquid separation to obtain ferric phosphate dihydrate and a lithium-containing filtrate;

[0029] (5) The ferric phosphate dihydrate precipitate obtained in step (4) is washed and dried to become regenerated ferric phosphate, and the lithium-containing filtrate is concentrated and reused in the lithium extraction process.

[0030] The method for recovering iron phosphate from lithium phosphate slag extracted from waste lithium iron phosphate positive and negative electrode mixtures is disclosed. The method recovers graphite by leaching metal ions with hydrochloric acid, and generates iron phosphate by oxidation and synthesis reaction. The residual lithium element in the lithium extraction slag can also be reused in the lithium extraction process. Multi-component recovery of lithium extraction slag from waste lithium iron phosphate positive and negative electrode mixtures is carried out, which provides a new method for the industrial treatment of lithium extraction slag from waste lithium iron phosphate positive and negative electrode mixtures.

[0031] Further, the concentration of the hydrochloric acid in step (1) is 25-40%, preferably 30-35%. The amount of hydrochloric acid used in step (1) is 1-1.4 times the theoretical value, preferably 1-1.2 times. The heating temperature of the heating reaction in step (1) is 40-80°C, preferably 50-60°C. The heating time of the heating reaction in step (1) is 1-4h, preferably 2-3h. The amount of iron powder in step (2) is 1-1.4 times the theoretical amount, preferably 1-1.2 times. The reaction stopping condition in step (2) is that the copper ion content is less than 10ppm and the aluminum ion content is less than 50ppm. The pH in step (2) is 3.2-3.4. The oxidant in step (3) includes oxygen, hydrogen peroxide, chlorine, etc., which can oxidize divalent iron to at least one of trivalent iron. The oxidation reaction temperature in step (3) is 40-80°C, preferably 50-60°C. The reaction time of the oxidation in step (3) is 10 to 30 minutes, preferably 15 to 20 minutes. The concentration of the diammonium phosphate in step (4) is 1.2 to 2 mol / L, preferably 1.6 to 1.8 mol / L. The phosphorus to iron ratio in step (4) is 0.96 to 1.02. The pH of the synthesis reaction in step (4) is controlled to be 1 to 3, preferably 1 to 2. The temperature of the synthesis reaction in step (4) is 40 to 100° C., preferably 60 to 80° C. The time of the synthesis reaction in step (4) is 30 to 90 minutes, preferably 60 to 80 minutes.

[0032] Embodiment 1

[0033] according to Figure 1 The schematic diagram of a process for recovering iron phosphate from lithium slag from waste lithium iron phosphate positive and negative electrode mixture is shown in FIG. The specific steps of this embodiment are as follows:

[0034] (1) Weigh 100 g of waste lithium iron phosphate positive and negative electrode mixture lithium slag and 1 L of 30% hydrochloric acid in a beaker, stir evenly and then slowly pour into the reactor;

[0035] (2) setting the temperature of the vacuum drying oven to 60° C. and the holding time to 3 h, placing the reactor in the vacuum drying oven to carry out metal ion leaching reaction, and leaching the metal elements in the lithium extraction slag;

[0036] (3) After the leaching reaction is completed, the filtrate and graphite slag are obtained by filtering with a circulating water vacuum filtration pump, and the graphite slag is washed with deionized water for multiple times until it is neutral, and can be used as a refractory material after drying;

[0037] (4) The copper ion and aluminum ion content of the filtrate is used to calculate the amount of iron powder required, and iron powder 1.2 times the theoretical value of iron powder is used to prepare an iron powder slurry with deionized water;

[0038] (5) stirring the filtrate with a magnetic stirrer, slowly adding iron powder slurry to the filtrate, and connecting a copper ion online detector and an aluminum ion online detector to the filtrate to test the copper ion and aluminum ion contents; stopping the addition of iron powder slurry when the copper ion content is lower than 10 ppm; adding sodium hydroxide solution to adjust the pH to 3.2-3.4 to form aluminum hydroxide precipitation; when the aluminum ion content is lower than 50 ppm, the reaction is terminated, and copper slag and aluminum slag are removed by solid-liquid separation to obtain an iron-rich liquid;

[0039] (6) controlling the temperature of the iron-rich liquid to 60° C., introducing oxygen gas into the iron-rich liquid for 20 min, oxidizing the ferrous chloride in the filtrate to ferric chloride, detecting the iron and phosphorus contents in the solution, and calculating the required ammonium dihydrogen phosphate;

[0040] (7) adding 1.8 mol / L ammonium dihydrogen phosphate to the filtrate to adjust the phosphorus-iron ratio to 1:1; introducing ammonia water to adjust the pH to 1-2, controlling the temperature to 60° C., reacting for 60 min to synthesize dihydrate iron phosphate precipitate, and performing solid-liquid separation to obtain dihydrate iron phosphate and lithium-containing filtrate;

[0041] (8) The ferric phosphate dihydrate precipitate is washed three times with deionized water and vacuum dried to become regenerated ferric phosphate. The lithium-containing filtrate can be reused in the lithium extraction process by evaporation and concentration.

[0042] (9) The iron, phosphorus, copper and aluminum contents of the regenerated iron phosphate were tested, and the iron-phosphorus ratio was calculated. The iron, phosphorus, copper and aluminum contents and the iron-phosphorus ratio of Example 1 are shown in Table 1. According to the test results, the iron and phosphorus contents, the iron-phosphorus ratio and the copper and aluminum impurity contents of the regenerated iron phosphate meet the industry standard HG / T6262-2024 for regenerated iron phosphate.

[0043] Table 1

[0044]

[0045] Embodiment 2

[0046] according to Figure 1 The schematic diagram of a process for recovering iron phosphate from lithium slag from waste lithium iron phosphate positive and negative electrode mixture is shown in FIG. The specific steps of this embodiment are as follows:

[0047] (1) Weigh 100 g of waste lithium iron phosphate positive and negative electrode mixture lithium slag and 1 L of 35% hydrochloric acid in a beaker, stir evenly and then slowly pour into the reactor;

[0048] (2) setting the temperature of the vacuum drying oven to 50° C. and the holding time to 4 h, placing the reactor in the vacuum drying oven to carry out metal ion leaching reaction, and leaching the metal elements in the lithium extraction slag;

[0049] (3) After the leaching reaction is completed, the filtrate and graphite slag are obtained by filtering with a circulating water vacuum filtration pump, and the graphite slag is washed with deionized water for multiple times until it is neutral, and can be used as a refractory material after drying;

[0050] (4) The copper ion and aluminum ion content of the filtrate is used to calculate the amount of iron powder required, and iron powder 1.1 times the theoretical value of iron powder is used to prepare an iron powder slurry with deionized water;

[0051] (5) stirring the filtrate with a magnetic stirrer, slowly adding iron powder slurry to the filtrate, and connecting a copper ion online detector and an aluminum ion online detector to the filtrate to test the copper ion and aluminum ion contents; stopping the addition of iron powder slurry when the copper ion content is lower than 10 ppm; adding sodium hydroxide solution to adjust the pH to 3.2-3.4 to form aluminum hydroxide precipitation; when the aluminum ion content is lower than 50 ppm, the reaction is terminated, and copper slag and aluminum slag are removed by solid-liquid separation to obtain an iron-rich liquid;

[0052] (6) controlling the temperature of the iron-rich liquid to 80° C., introducing oxygen gas into the iron-rich liquid for 10 min, oxidizing the ferrous chloride in the filtrate to ferric chloride, detecting the iron and phosphorus contents in the solution, and calculating the required ammonium dihydrogen phosphate;

[0053] (7) adding 1.6 mol / L ammonium dihydrogen phosphate to the filtrate to adjust the phosphorus-iron ratio to 1:1; introducing ammonia water to adjust the pH to 1-2, controlling the temperature to 80° C., reacting for 80 min to synthesize dihydrate iron phosphate precipitate, and performing solid-liquid separation to obtain dihydrate iron phosphate and lithium-containing filtrate;

[0054] (8) The ferric phosphate dihydrate precipitate is washed three times with deionized water and vacuum dried to become regenerated ferric phosphate. The lithium-containing filtrate can be reused in the lithium extraction process by evaporation and concentration.

[0055] (9) The iron, phosphorus, copper and aluminum contents of the regenerated iron phosphate were tested, and the iron-phosphorus ratio was calculated. The iron, phosphorus, copper and aluminum contents and the iron-phosphorus ratio of Example 2 are shown in Table 1. According to the test results, the iron and phosphorus contents, the iron-phosphorus ratio and the copper and aluminum impurity contents of the regenerated iron phosphate meet the industry standard HG / T6262-2024 for regenerated iron phosphate.

[0056] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0057] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for recovering iron phosphate from waste lithium iron phosphate positive and negative electrode mixed lithium slag, characterized in that: The following steps are involved: Step 1, placing the waste lithium iron phosphate positive and negative electrode mixed lithium extraction slag and hydrochloric acid in a reactor to leach the metal elements therein, and filtering to obtain a filtrate and graphite slag; Step 2: Detect the contents of copper ions and aluminum ions in the filtrate, calculate the required amount of iron powder, add iron powder to the filtrate to remove the copper ions in the filtrate, adjust the pH to remove the aluminum ions, and then use an oxidant to oxidize the divalent iron in the filtrate to trivalent iron; Step 3, adding ammonia water and diammonium phosphate to the filtrate, wherein the ammonia water is used to adjust the pH, and the diammonium phosphate is used to adjust the iron-phosphorus ratio to 0.96-1.02, synthesizing dihydrate iron phosphate precipitate through a synthesis reaction, and performing solid-liquid separation to obtain dihydrate iron phosphate and a lithium-containing filtrate; Step 4: The ferric phosphate dihydrate precipitate is washed and dried to become regenerated ferric phosphate.

2. The method for recovering iron phosphate from mixed lithium slag of waste lithium iron phosphate positive and negative electrodes as claimed in claim 1, characterized in that: The concentration of the hydrochloric acid is 25-40%, and the actual usage of the hydrochloric acid is 1-1.4 times of the theoretical usage.

3. The method for recovering iron phosphate from mixed lithium phosphate slag from waste lithium iron phosphate positive and negative electrodes as claimed in claim 2, characterized in that: The reaction temperature of the hydrochloric acid leaching is 40-80° C., and the reaction time is 1-4 hours.

4. The method for recovering iron phosphate from mixed lithium slag of waste lithium iron phosphate positive and negative electrodes as claimed in claim 1, characterized in that: The oxidant is at least one of oxygen, hydrogen peroxide and chlorine.

5. The method for recovering iron phosphate from mixed lithium phosphate slag from waste lithium iron phosphate positive and negative electrodes as claimed in claim 4, characterized in that: The oxidation time is 10 to 30 minutes, and the oxidation temperature is 40 to 80°C.

6. The method for recovering iron phosphate from mixed lithium phosphate slag from waste lithium iron phosphate positive and negative electrodes as claimed in claim 1, characterized in that: The temperature of the synthesis reaction is 40-100° C., and the time of the synthesis reaction is 30-90 minutes.

7. The method for recovering iron phosphate from mixed lithium slag of waste lithium iron phosphate positive and negative electrodes as claimed in claim 6, characterized in that: The pH of the synthesis reaction is 1-3.

8. The method for recovering iron phosphate from mixed lithium phosphate slag from waste lithium iron phosphate positive and negative electrodes as claimed in claim 1, characterized in that: The concentration of the diammonium phosphate is 1.2-2 mol / L.

9. Application of the method for recovering iron phosphate from mixed lithium slag of waste lithium iron phosphate positive and negative electrodes, characterized in that: The graphite slag obtained in step one is used as a refractory material after washing and drying, and the lithium-containing filtrate obtained in step three is concentrated and used to extract lithium elements.

10. Application of the method for recovering iron phosphate from mixed lithium slag of waste lithium iron phosphate positive and negative electrodes, characterized in that: Valuable elements are recovered from the mixed lithium extraction slag of waste lithium iron phosphate positive and negative electrodes using the method for recovering iron phosphate from the mixed lithium extraction slag of waste lithium iron phosphate positive and negative electrodes as described in any one of claims 1 to 8.

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