Method for extracting iron element by using lithium extraction slag and application

Abstract

The invention provides a method for extracting an iron element by utilizing lithium extraction slag and application, the lithium extraction slag is calcined in air atmosphere, carbon impurities and sulfur impurities in the lithium extraction slag are removed, and ferric phosphate in the lithium extraction slag is oxidized and decomposed into ferric oxide and phosphate; ferric oxide and phosphate are placed in a phosphoric acid solution to leach metal ions, and aluminum impurities react with phosphoric acid to generate an aluminum dihydrogen phosphate solution; adding iron powder into the aluminum dihydrogen phosphate solution to replace aluminum impurities to generate aluminum-containing slag, and removing the aluminum impurities through solid-liquid separation to obtain a residual solution; placing the residual solution containing iron and phosphorus in a reaction kettle, adding phosphoric acid to adjust the ratio of iron to phosphorus, and generating an iron phosphate precursor through a hydrothermal reaction; and sequentially carrying out suction filtration, washing and firing on the obtained iron phosphate precursor to obtain iron phosphate. Under the condition that new impurities are not introduced, the iron element in the waste lithium iron phosphate lithium extraction slag is recycled, and iron phosphate is generated. The economic benefit and the social benefit of recycling the waste lithium iron phosphate battery are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery recycling, and specifically relates to a method and application of extracting iron elements by utilizing lithium extraction slag. Background Art

[0002] At present, the main process for industrial recycling of lithium iron phosphate is hydrometallurgy. The main products are lithium salts and battery-grade lithium carbonate. However, it must be emphasized that current industrial technology is mainly focused on recovering lithium from waste lithium iron phosphate. Although the lithium slag after lithium extraction is rich in iron and phosphorus elements, it is usually considered useless because it contains carbon impurities, sulfur impurities, aluminum impurities, etc., and is piled up and stored in warehouses, which causes a lot of resource waste and environmental problems. In order to improve the economic and social benefits of lithium iron phosphate battery recycling, it is necessary to develop a method for recycling lithium iron phosphate lithium slag. Summary of the invention

[0003] The purpose of the present invention is to provide a method and application of extracting iron from lithium phosphate slag. The method removes carbon, sulfur and aluminum impurities from waste lithium iron phosphate slag by high-temperature calcination in air and iron powder replacement; recovers iron from waste lithium iron phosphate slag without introducing new impurities through phosphoric acid leaching and phosphoric acid synthesis to generate iron phosphate. The economic and social benefits of recycling waste lithium iron phosphate batteries are improved. The specific scheme is as follows:

[0004] According to a first aspect of the present invention, one or more embodiments of the present application provide a method for extracting iron using lithium extraction slag, comprising:

[0005] Step 1, calcining the lithium extraction slag in an air atmosphere to remove carbon impurities and sulfur impurities in the lithium extraction slag, and oxidizing and decomposing the iron phosphate in the lithium extraction slag into iron sesquioxide and phosphate;

[0006] Step 2, placing ferric oxide and phosphate in a phosphoric acid solution to leach metal ions, wherein aluminum impurities react with phosphoric acid to form aluminum dihydrogen phosphate solution;

[0007] Step 3, adding iron powder to the aluminum dihydrogen phosphate solution to replace aluminum impurities, generating aluminum-containing slag, removing aluminum impurities by solid-liquid separation, and obtaining a residual solution;

[0008] Step 4, placing the remaining solution containing iron and phosphorus in a reaction kettle, adding phosphoric acid to adjust the iron-phosphorus ratio, and generating an iron phosphate precursor through a hydrothermal reaction;

[0009] Step 5: The obtained iron phosphate precursor is filtered, washed and calcined in sequence to obtain iron phosphate.

[0010] According to the above technical solution of the present invention, the following improvements can also be made:

[0011] Wherein, the lithium extraction slag in the step 1 is calcined at a temperature of 550-750° C. in an air atmosphere, and the calcination time is 2-8 hours.

[0012] During the calcination process, the calcination is stopped when the lithium extraction slag turns into a reddish brown powder, and then the amount of ferric oxide generated is tested by ICP-OES for later use.

[0013] Among them, in the step 2, a theoretical amount of phosphoric acid solution is prepared based on the amount of ferric oxide obtained, and the actual amount of phosphoric acid solution is 1-1.5 times the theoretical amount. The actual amount of phosphoric acid solution is slowly added to the obtained reddish-brown powder, and stirred with a magnetic stirrer until the reddish-brown powder is dissolved in the phosphoric acid solution, and then the iron-rich liquid is obtained by solid-liquid separation.

[0014] Wherein, the solid-liquid ratio of the phosphoric acid solution is 5 to 15 mL / g.

[0015] The theoretical amount of iron powder in step three is obtained based on the aluminum content in the aluminum dihydrogen phosphate solution, and the actual amount of iron powder is 1 to 2 times the theoretical amount.

[0016] Wherein, in the step 4, during the process of adding phosphoric acid to adjust the iron-phosphorus ratio, the molar ratio of ferric oxide to phosphoric acid is 1:4, and the concentration of the phosphoric acid solution is 20-60%.

[0017] Wherein, in the step 4, the hydrothermal reaction temperature is 60-90° C., and the reaction time is 2-8 hours.

[0018] The iron phosphate precursor generated by the hydrothermal reaction is filtered, washed three times with deionized water, and then calcined to obtain the iron phosphate.

[0019] According to the second aspect of the present invention, one or more embodiments in the present application provide an application of a method for extracting iron elements using lithium extraction slag, and a method for extracting iron elements using lithium extraction slag as described in any one of the above items is used to recover iron elements in waste lithium iron phosphate lithium extraction slag.

[0020] The beneficial effects of the present invention are:

[0021] Compared with the prior art, the present invention provides a method and application of extracting iron elements from lithium extraction slag, wherein carbon impurities and sulfur impurities in waste lithium iron phosphate lithium extraction slag are removed by calcination in an air atmosphere, and iron phosphate is oxidized and decomposed into ferric oxide and phosphate; without introducing new impurities, aluminum impurities are removed by phosphoric acid leaching and iron powder replacement, and finally new iron phosphate is hydrothermally synthesized. The process of the embodiment of the present application is simple, and waste lithium iron phosphate lithium extraction slag is recycled and utilized without introducing new impurities, thereby increasing the economic and environmental benefits of recycling waste lithium iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a method for extracting iron elements by using lithium extraction slag and a schematic flow chart of its application. DETAILED DESCRIPTION

[0023] 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.

[0024] 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.

[0025] As attached Figure 1 As shown, this embodiment provides a method and application of extracting iron using lithium extraction slag, the method comprising the following steps:

[0026] (1) placing the waste lithium iron phosphate slag in a muffle furnace and calcining it for a certain period of time in an air atmosphere until the black waste lithium iron phosphate slag turns into a reddish brown powder, and measuring the amount of ferric oxide generated by ICP-OES;

[0027] (2) slowly pouring the prepared phosphoric acid into the beaker containing the reddish brown powder obtained in step (1), stirring with a magnetic stirrer, controlling the temperature, time, and magnetic stirring speed until the reddish brown powder is substantially dissolved in the solution, and obtaining an iron-rich liquid by solid-liquid separation;

[0028] (3) testing the aluminum content in the iron-rich solution by ICP-OES, calculating the theoretical value of adding iron powder, adding an appropriate amount of iron powder to the iron-rich solution to replace aluminum impurities, generating aluminum-containing slag, removing aluminum impurities by solid-liquid separation, and obtaining an aluminum-removing solution;

[0029] (4) according to the condition that the molar ratio of ferric oxide to phosphoric acid is 1:4, the dosage of phosphoric acid is determined, the aluminum removal solution is placed in a reaction kettle, phosphoric acid is added to adjust the iron-phosphorus ratio, after stirring for a period of time, the solution is placed in a vacuum drying oven to generate an iron phosphate precursor through a hydrothermal reaction;

[0030] (5) The iron phosphate precursor generated by the hydrothermal reaction is filtered, washed, and calcined at high temperature to obtain iron phosphate.

[0031] The method for recycling waste lithium iron phosphate slag for lithium extraction, which recovers iron elements in waste lithium iron phosphate slag for lithium extraction and generates iron phosphate through phosphoric acid leaching and phosphoric acid synthesis without introducing new impurities. The waste lithium iron phosphate slag for lithium extraction is used to generate new iron phosphate, thereby improving the economic and environmental benefits of recycling waste lithium iron phosphate by hydrometallurgy.

[0032] Furthermore, the calcination temperature in step (1) is 500-700°C, preferably 550-600°C.

[0033] Furthermore, the calcination time in step (1) is 2 to 8 hours, preferably 4 to 6 hours.

[0034] Furthermore, the amount of phosphoric acid used in step (2) is 1 to 1.5 times the theoretical amount, preferably 1.1 to 1.2 times, calculated based on the metal element content in the reddish-brown powder.

[0035] Furthermore, the solid-to-liquid ratio of the phosphoric acid leaching in step (2) is 5 to 15 mL / g; preferably 8 to 10 mL / g.

[0036] Furthermore, the leaching time of the phosphoric acid leaching in step (2) is 1 to 8 hours, preferably 4 to 6 hours.

[0037] Furthermore, the reaction temperature of the phosphoric acid leaching in step (2) is 60 to 100°C, preferably 80 to 90°C.

[0038] Furthermore, the amount of iron powder used in step (3) is calculated based on the aluminum content in the acid leaching solution and is 1 to 2 times the theoretical amount; preferably 1.2 to 1.5 times.

[0039] Furthermore, in the replacement reaction in step (3), the pH of the solution is 1.5 to 3.5, preferably 2 to 3.

[0040] Furthermore, the replacement reaction in step (3) has a reaction time of 1 to 5 hours, preferably 2 to 4 hours.

[0041] Furthermore, in the replacement reaction in step (3), the rotation speed of the magnetic stirring is 300 to 700 r / min, preferably 500 to 600 r / min.

[0042] Furthermore, in step (4), the phosphoric acid is used to adjust the iron-phosphorus ratio, the molar ratio of ferric oxide to phosphoric acid is 1:4, and the concentration of phosphoric acid is 20-60%, preferably 40-50%.

[0043] Furthermore, the stirring speed of the magnetic stirring of the phosphoric acid and the aluminum removal liquid in step (4) is 300 to 700 r / min, preferably 500 to 600 r / min.

[0044] Furthermore, the magnetic stirring time of the phosphoric acid and the aluminum removal liquid in step (4) is 30 to 150 minutes, preferably 60 to 120 minutes.

[0045] Furthermore, the hydrothermal reaction temperature in step (4) is 60 to 90°C; preferably 70 to 80°C.

[0046] Furthermore, the hydrothermal reaction aging reaction time in step (4) is 2 to 8 hours, preferably 4 to 6 hours.

[0047] Furthermore, the washing times in step (4) is 1 to 5 times; preferably 3 to 4 times.

[0048] In order to more intuitively describe the technical solution and effect of this embodiment, the following two specific embodiments are used for illustration:

[0049] Embodiment 1

[0050] (1) Weigh 200 g of waste lithium iron phosphate lithium extraction slag and place it in a muffle furnace, set the heating rate to 10°C / min, the heating time to 55 min, and maintain it for 180 min; after the program is completed, naturally cool to room temperature, take out the reddish brown powder, and measure the carbon content and sulfur content of the waste lithium iron phosphate lithium extraction slag and the reddish brown powder by a high-frequency infrared sulfur-carbon analyzer; the carbon and sulfur removal rates of the lithium extraction slag are shown in Table 2;

[0051] (2) Testing the amount of iron in the powder by ICP-OES, calculating the amount of ferric oxide, and preparing a phosphoric acid solution;

[0052] (3) In a fume hood, slowly pour 1000 ml of the prepared 1.2 times theoretical amount of phosphoric acid solution into a beaker containing 100 g of reddish brown powder, stir with a heated magnetic stirrer, set the temperature to 80° C., the time to 4 h, and the stirring speed to 500 r / min, until the reddish brown powder is basically dissolved in the solution, and obtain an iron-rich liquid by solid-liquid separation;

[0053] (4) testing the aluminum content in the iron-rich solution by ICP-OES, calculating the theoretical value of the added iron powder, adding 1.2 times the theoretical value of iron powder to the iron-rich solution, stirring by heating with a magnetic stirrer, controlling the pH to 2-3, the reaction time to 3 h, the stirring speed to 500 r / min, and removing aluminum impurities by solid-liquid separation after the reaction to obtain an aluminum removal solution;

[0054] (5) Calculate the amount of phosphoric acid to be added based on the condition that the molar ratio of ferric oxide to phosphoric acid is 1:4, wherein the concentration of phosphoric acid is 40%;

[0055] (6) placing the dealuminized solution in a reaction kettle, adding phosphoric acid to adjust the iron-phosphorus ratio to 0.96-1, stirring with magnetic stirring at a speed of 500 r / min for 60 min, placing in a 90° C. vacuum drying oven, and reacting for 4 h; after the reaction is completed, obtaining an iron phosphate precursor by solid-liquid separation;

[0056] (7) The iron phosphate precursor generated by the hydrothermal reaction was washed three times with deionized water and calcined at high temperature to obtain iron phosphate. The iron and phosphorus contents of the iron phosphate were tested by ICP-OES, and the iron-phosphorus ratio was calculated. The iron-phosphorus ratio of Example 1 is shown in Table 1.

[0057] Table 1

[0058] Iron (Fe) w% Phosphorus (P) w% Iron:phosphorus ratio (Fe:P) Embodiment 1 36.40 20.60 0.98 Embodiment 2 36.21 20.49 0.97

[0059] Embodiment 2

[0060] (1) Weigh 200 g of waste lithium iron phosphate lithium extraction slag and place it in a muffle furnace, set the heating rate to 10°C / min, the heating time to 50 min, and maintain it for 150 min; after the program is completed, naturally cool it to room temperature, take out the reddish brown powder, and measure the carbon content and sulfur content of the waste lithium iron phosphate lithium extraction slag and the reddish brown powder by a high-frequency infrared sulfur-carbon analyzer; the carbon and sulfur removal rates of the lithium extraction slag are shown in Table 2;

[0061] (2) Testing the amount of iron in the powder by ICP-OES, calculating the amount of ferric oxide, and preparing a phosphoric acid solution;

[0062] (3) In a fume hood, slowly pour 1000 ml of the prepared 1.2 times theoretical amount of phosphoric acid solution into a beaker containing 100 g of reddish brown powder, stir with a heated magnetic stirrer, set the temperature to 70° C., the time to 5 h, and the stirring speed to 600 r / min, until the reddish brown powder is basically dissolved in the solution, and obtain an iron-rich liquid by solid-liquid separation;

[0063] (4) testing the aluminum content in the iron-rich solution by ICP-OES, calculating the theoretical value of the added iron powder, adding 1.2 times the theoretical value of iron powder to the iron-rich solution, stirring by a heated magnetic stirrer, controlling the pH to 2-3, the reaction time to 4 h, the stirring speed to 600 r / min, and removing aluminum impurities by solid-liquid separation after the reaction to obtain an aluminum removal solution;

[0064] (5) Calculate the amount of phosphoric acid to be added based on the condition that the molar ratio of ferric oxide to phosphoric acid is 1:4, wherein the concentration of phosphoric acid is 50%;

[0065] (6) placing the dealuminized solution in a reaction kettle, adding phosphoric acid to adjust the iron-phosphorus ratio to 0.96-1, stirring with magnetic stirring at a speed of 600 r / min for 90 min, placing in a vacuum drying oven at 80° C., and reacting for 3 h; after the reaction is completed, obtaining an iron phosphate precursor by solid-liquid separation;

[0066] (7) The iron phosphate precursor generated by the hydrothermal reaction was washed three times with deionized water and calcined at high temperature to obtain iron phosphate. The iron and phosphorus contents of the iron phosphate were tested by ICP-OES, and the iron-to-phosphorus ratio was calculated. The iron-to-phosphorus ratio of Example 2 is shown in Table 1.

[0067] Table 2

[0068]

[0069] In the above embodiments, the amount of each component is determined based on the corresponding reaction formula. Specifically, the theoretical amount of phosphoric acid solution is calculated according to the chemical reaction equation:

[0070] 2Fe2O3+6H3PO4→4FePO4+3H2O+O2↑

[0071] Calculate the theoretical amount of iron powder according to the chemical reaction equation:

[0072] 2Al+6H3PO4→2Al(H2PO4)3+3H2

[0073] Al(H2PO4)3+Fe→Al↓+Fe(H2PO4)3

[0074] The reason why it is greater than the theoretical amount is that during the experiment or implementation process, changes in the experimental or implementation conditions, such as temperature, pressure, etc., may affect the reaction efficiency of the reagent, thereby requiring an increase in the amount of the reagent.

[0075] 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.

[0076] 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 extracting iron using lithium extraction slag, characterized in that: The following steps are involved: Step 1, calcining the lithium extraction slag in an air atmosphere to remove carbon impurities and sulfur impurities in the lithium extraction slag, and oxidizing and decomposing the iron phosphate in the lithium extraction slag into iron sesquioxide and phosphate; Step 2, placing ferric oxide and phosphate in a phosphoric acid solution to leach metal ions, wherein aluminum impurities react with phosphoric acid to form aluminum dihydrogen phosphate solution; Step 3, adding iron powder to the aluminum dihydrogen phosphate solution to replace aluminum impurities, generating aluminum-containing slag, removing aluminum impurities by solid-liquid separation, and obtaining a residual solution; Step 4, placing the remaining solution containing iron and phosphorus in a reaction kettle, adding phosphoric acid to adjust the iron-phosphorus ratio, and generating an iron phosphate precursor through a hydrothermal reaction; Step 5: The obtained iron phosphate precursor is filtered, washed and calcined in sequence to obtain iron phosphate.

2. The method for extracting iron from lithium-extracting slag as claimed in claim 1, characterized in that: The lithium extraction slag in the step 1 is calcined at a temperature of 550-750° C. in an air atmosphere, and the calcination time is 2-8 hours.

3. A method for extracting iron using lithium extraction slag as claimed in claim 2, characterized in that: During the calcination process, the calcination is stopped when the lithium extraction slag becomes a reddish brown powder, and then the amount of ferric oxide generated is tested by ICP-OES for later use.

4. A method for extracting iron using lithium extraction slag as claimed in claim 3, characterized in that: In the step 2, a theoretical amount of phosphoric acid solution is prepared based on the amount of ferric oxide obtained, and the actual amount of phosphoric acid solution is 1-1.5 times the theoretical amount. The actual amount of phosphoric acid solution is slowly added to the obtained reddish-brown powder, and stirred with a magnetic stirrer until the reddish-brown powder is dissolved in the phosphoric acid solution, and then an iron-rich liquid is obtained by solid-liquid separation.

5. A method for extracting iron using lithium extraction slag as claimed in claim 4, characterized in that: The solid-to-liquid ratio of the phosphoric acid solution is 5 to 15 mL / g.

6. The method for extracting iron from lithium-extracting slag as claimed in claim 1, characterized in that: The theoretical amount of iron powder in step three is obtained based on the aluminum content in the aluminum dihydrogen phosphate solution, and the actual amount of iron powder is 1 to 2 times the theoretical amount.

7. The method for extracting iron from lithium-extracting slag as claimed in claim 1, characterized in that: In the step 4, during the process of adding phosphoric acid to adjust the iron-phosphorus ratio, the molar ratio of ferric oxide to phosphoric acid is 1:4, and the concentration of the phosphoric acid solution is 20-60%.

8. The method for extracting iron from lithium-extracting slag as claimed in claim 7, characterized in that: In the step 4, the hydrothermal reaction temperature is 60 to 90° C., and the reaction time is 2 to 8 hours.

9. A method for extracting iron using lithium extraction slag as claimed in claim 8, characterized in that: The iron phosphate precursor generated by the hydrothermal reaction is filtered, washed at least three times with deionized water, and then calcined to obtain iron phosphate.

10. An application of a method for extracting iron using lithium extraction slag, characterized in that: The method for extracting iron from lithium extraction slag as described in any one of claims 1 to 9 is used to recover iron from waste lithium iron phosphate lithium extraction slag.

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