Method for recovering lithium and iron phosphate from aerobically roasted lithium iron phosphate battery
By acid leaching and lithium precipitation reaction of lithium iron phosphate battery powder, the problem of low lithium recovery rate is solved, efficient and low-cost lithium and iron phosphate recovery is achieved, and the generation of by-products is reduced.
Patent Information
- Application Number
- CN202510875976.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-09-19
AI Technical Summary
When recycling lithium iron phosphate batteries, the existing technology has a low lithium recovery rate, lithium elements remain in the leaching residue, and a large amount of acid and alkali is required, resulting in high costs and many by-products.
By acid leaching the oxygen-roasted lithium iron phosphate battery powder, adjusting the pH value to 0-0.5, using LiFePO4 to consume excess acid to adjust the pH to 1-2, performing solid-liquid separation, obtaining lithium liquid and iron phosphate slag, and then performing lithium precipitation reaction to achieve efficient lithium recovery.
The comprehensive recovery rate of lithium is improved, the recovery cost is reduced, the by-products are reduced, and the economic profit is increased.
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Figure CN120664568A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of waste battery recycling, and in particular to a method for recovering lithium and iron phosphate from lithium iron phosphate batteries subjected to oxygen roasting. Background Art
[0002] At present, the mainstream pretreatment process for recycling waste lithium iron phosphate batteries is discharge-disassembly-crushing-roasting-sorting, in which roasting mainly removes organic matter (such as electrolyte, binder and diaphragm, etc.) and decomposes harmful substances through high temperature. During the aerobic roasting process, the Fe contained in LiFePO4 2+ It will be oxidized to generate Li3Fe2(PO4)3 and Fe2O3. The existing technology often uses acid with pH = 1 to 2 to extract lithium. The lithium recovery rate of this method is low, and there is still a lot of lithium elements remaining in the leaching residue.
[0003] In view of this, the present invention is proposed. Summary of the Invention
[0004] The object of the present invention is to provide a method for recovering lithium and iron phosphate from an aerobic roasted lithium iron phosphate battery, so as to solve or improve the above technical problems.
[0005] The present invention can be achieved like this:
[0006] In a first aspect, the present invention provides a method for recovering lithium and iron phosphate from an aerobic-roasted lithium iron phosphate battery, comprising the following steps:
[0007] The oxygen-roasted lithium iron phosphate battery powder is reacted with acid to obtain an acid leaching slurry with a pH value of 0 to 0.5;
[0008] The acid leaching slurry is mixed with oxygen-free roasted lithium iron phosphate battery powder and an oxidant to obtain a mixed slurry with a pH value of 1 to 2; the mixed slurry is subjected to solid-liquid separation to obtain iron phosphate slag and lithium liquid;
[0009] The ferric phosphate slag is acid-dissolved and solid-liquid separated to obtain graphite slag and ferrophosphorus solution; the ferrophosphorus solution is mixed with anhydrous ferric phosphate seed crystals and aged to obtain ferric phosphate dihydrate; the ferric phosphate dihydrate is calcined to obtain anhydrous ferric phosphate;
[0010] The lithium solution is reacted with alkali and carbonate to precipitate lithium, and the solid-liquid is separated to obtain lithium carbonate.
[0011] In an optional embodiment, the lithium element in the lithium iron phosphate battery powder and the H in the acid are oxygen-roasted. + The molar ratio is 1:3.15 to 1:3.6.
[0012] In an optional embodiment, the oxygen-roasted lithium iron phosphate battery powder is first mixed with water to obtain a first intermediate slurry; and then the first intermediate slurry is mixed with acid to obtain an acid leaching slurry.
[0013] In an optional embodiment, the liquid-to-solid ratio of water to aerobic-calcined lithium iron phosphate battery powder is 1 mL:1 g to 2 mL:1 g.
[0014] In an optional embodiment, the molar amount of lithium element in the oxygen-free calcined lithium iron phosphate battery powder is 0.6 times to 0.65 times the total molar amount of iron element in the acid leaching slurry.
[0015] In an optional embodiment, the amount of oxidant added is to reduce the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder. 2+ Completely oxidized to Fe 3+ 1.2 to 1.5 times the theoretical amount required.
[0016] In an alternative embodiment, the oxidizing agent comprises at least one of hydrogen peroxide, ozone, and sulfur dioxide.
[0017] In an alternative embodiment, the oxidizing agent is hydrogen peroxide.
[0018] In an optional embodiment, the oxygen-free roasted lithium iron phosphate battery powder is mixed with water to obtain a second intermediate slurry; the acid leaching slurry is mixed with the second intermediate slurry to obtain a third intermediate slurry; and an oxidant is added to the third intermediate slurry to obtain a mixed slurry.
[0019] In an optional embodiment, the liquid-to-solid ratio of water to oxygen-free calcined lithium iron phosphate battery powder is 1 mL:1 g to 2 mL:1 g.
[0020] In an alternative embodiment, the addition rate of the oxidant is 1 mL / min to 2 mL / min.
[0021] In an optional embodiment, the aging temperature is 90° C. to 100° C., and the aging time is 4 h to 6 h.
[0022] In an optional embodiment, the calcination temperature is 400° C. to 500° C., and the calcination time is 2 h to 3 h.
[0023] In an optional embodiment, the temperature of lithium deposition is not less than 80° C., and the time is 2 h to 3 h.
[0024] The beneficial effects of the present invention include:
[0025] The present invention provides a method for recovering lithium and iron phosphate from an oxygen-roasted lithium iron phosphate battery. First, the oxygen-roasted lithium iron phosphate battery powder is acid-leached to obtain an acid-leaching slurry with a pH of 0 to 0.5, so that the Fe in the oxygen-roasted lithium iron phosphate battery powder is recovered. 3+The method uses excess acid to calcine the LiFePO4 in the lithium iron phosphate battery powder to consume the excess acid in the acid leaching slurry to adjust the pH to 1-2, so that iron and phosphorus are precipitated to obtain lithium liquid and iron phosphate slag. + 、Fe 3+ PO4 3+ Converted into free ions, thus ensuring that all Li elements are leached out, and then the pH value is adjusted with LiFePO4 to make Fe 3+ PO4 3+ Re-formation of precipitation, LiFePO4 adjusts the pH value while releasing Li + 、Fe 2+ PO4 3+ To the liquid phase, complete the Li extraction, so as to achieve the recovery and utilization of excess acid in the acid leaching slurry, improve the comprehensive lithium recovery rate, and avoid the increase of by-products by adding additional alkali, greatly reduce the recovery cost and improve economic profits. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.
[0027] Figure 1 This is a main process flow chart of the method for recovering lithium and iron phosphate from aerobic roasted lithium iron phosphate batteries provided by the present invention. DETAILED DESCRIPTION
[0028] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.
[0029] The method for recovering lithium and iron phosphate from an aerobic-roasted lithium iron phosphate battery provided by the present invention is described in detail below.
[0030] In battery recycling technology, batteries need to be roasted after crushing to remove residual electrolyte. The roasting process is divided into anaerobic roasting and aerobic roasting. Anaerobic roasting is carried out in an inert gas environment, and the main component of battery powder is LiFePO4; aerobic roasting is carried out in an oxygen / air atmosphere, and part of the LiFePO4 is oxidized to Li3Fe2(PO4)3.
[0031] The present invention provides a method for recovering lithium and iron phosphate from lithium iron phosphate batteries by oxygen roasting. Figure 1 , including the following steps:
[0032] S1: reacting oxygen-calcined lithium iron phosphate battery powder with acid to obtain an acid leaching slurry with a pH value of 0 to 0.5.
[0033] In this step, the Fe in the oxygen-roasted lithium iron phosphate battery powder is acid-leached. 3+ and phosphate exist in the liquid phase in a free state.
[0034] The chemical reactions involved in this step include: 2Li3Fe2(PO4)3+9H2SO4→3Li2SO4+2Fe2(SO4)3+6H3PO4.
[0035] In some optional embodiments, the lithium element in the lithium iron phosphate battery powder and the H in the acid are calcined by oxygen. + The molar ratio can be 1:3.15 to 1:3.6, such as 1:3.15, 1:3.2, 1:3.3, 1:3.4, 1:3.5 or 1:3.6, or other values within the range of 1:3.15 to 1:3.6.
[0036] If the lithium element in the lithium iron phosphate battery powder is oxygen-roasted and the H + The molar ratio of is less than 1:3.15 (such as 1:3), which is not conducive to the leaching of lithium elements; if the elements in the lithium iron phosphate battery powder are calcined with oxygen and H + The molar ratio is greater than 1:3.6 (such as 1:4), and the pH value in the subsequent adjustment process is low, which is not conducive to the precipitation of iron and phosphorus.
[0037] In some optional embodiments, the pH value of the acid leaching slurry may be 0, 0.1, 0.2, 0.3, 0.4 or 0.5, or other values within the range of 0 to 0.5.
[0038] If the pH value of the acid leaching slurry is greater than 0.5, it is likely to result in a low lithium leaching rate.
[0039] In some optional embodiments, the acid leaching process can be carried out at room temperature, and the acid leaching time can be determined by detecting the Fe 3+ and Fe 2+ ion content, when the acid leaching solution contains Fe 3 When the content no longer increases and remains substantially stable, the acid leaching process can be terminated. The acid used in the acid leaching process can be, for example, sulfuric acid. Furthermore, the acid leaching can be performed under stirring conditions, with a stirring speed of, for example, 250 to 350 r / min.
[0040] In some optional embodiments, the oxygen-roasted lithium iron phosphate battery powder can be first mixed with water to prepare a first intermediate slurry; then the first intermediate slurry is mixed with acid to obtain an acid leaching slurry. This method can be more conducive to improving Li+ than directly reacting the oxygen-roasted lithium iron phosphate battery powder with acid. + leaching rate.
[0041] The liquid-to-solid ratio of the water to the aerobic-calcined lithium iron phosphate battery powder can be illustratively 1 mL:1 g to 2 mL:1 g, such as 1 mL:1 g, 1.5 mL:1 g or 2 mL:1 g, or other values within the range of 1 mL:1 g to 2 mL:1 g.
[0042] S2: mixing the acid leaching slurry with oxygen-free roasted lithium iron phosphate battery powder and an oxidant to obtain a mixed slurry with a pH value of 1 to 2; performing solid-liquid separation on the mixed slurry to obtain iron phosphate slag and lithium liquid.
[0043] The LiFePO4 in the lithium iron phosphate battery powder is calcined with oxygen to consume the excess acid in the acid leaching slurry to adjust the pH to 1-2, so that iron and phosphorus are precipitated to obtain lithium liquid and iron phosphate slag.
[0044] The chemical reactions involved in this step include: Fe2(SO4)3+3H3PO4+6LiFePO4+3H2O2→3Li2SO4+8FePO4+6H2O.
[0045] In some optional embodiments, the molar amount of lithium element in the oxygen-free calcined lithium iron phosphate battery powder is 0.6 times to 0.65 times the total molar amount of iron element in the acid leaching slurry, such as 0.6 times, 0.61 times, 0.62 times, 0.63 times, 0.64 times or 0.65 times, etc., and can also be other values within the range of 0.6 times to 0.65 times.
[0046] In some optional embodiments, the amount of oxidant added is to reduce the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder. 2+ Completely oxidized to Fe 3+ 1.2 to 1.5 times of the required theoretical amount, such as 1.2 times, 1.25 times, 1.3 times, 1.35 times, 1.4 times, 1.45 times or 1.5 times, etc., can also be other values within the range of 1.2 to 1.5 times.
[0047] By setting the amount of the oxidant within the above range, it is possible to ensure that Fe 2+ Completely oxidized to Fe 3+ .
[0048] In some optional embodiments, the oxidant may illustratively include at least one of hydrogen peroxide, ozone, and sulfur dioxide. In some more typical embodiments, the oxidant may be hydrogen peroxide, which can avoid the introduction of impurities and does not require additional decontamination treatment.
[0049] In some optional embodiments, the pH value of the mixed slurry may be 1, 1.5, or 2, or other values within the range of 1 to 2.
[0050] If the pH value of the mixed slurry is less than 1, it is not conducive to the precipitation of iron and phosphorus; if the pH value of the mixed slurry is greater than 2, the comprehensive leaching rate of lithium is low.
[0051] In some optional embodiments, the oxygen-free roasted lithium iron phosphate battery powder can be mixed with water to obtain a second intermediate slurry; the acid-leached slurry is mixed with the second intermediate slurry to obtain a third intermediate slurry; and an oxidant is added to the third intermediate slurry to obtain a mixed slurry. Following this mixing sequence can achieve a higher recovery rate.
[0052] Among them, the liquid-solid ratio of water to oxygen-free calcined lithium iron phosphate battery powder can be 1mL:1g to 2mL:1g, such as 1mL:1g, 1.5mL:1g or 2mL:1g, etc., or other values within the range of 1mL:1g to 2mL:1g.
[0053] The acid leaching slurry and the second intermediate slurry may be mixed under stirring conditions, and the stirring speed may be, for example, 250 r / min to 350 r / min.
[0054] In some optional embodiments, the addition rate of the oxidant can be 1 mL / min to 2 mL / min, such as 1 mL / min, 1.5 mL / min or 2 mL / min, or other values within the range of 1 mL / min to 2 mL / min.
[0055] Taking hydrogen peroxide as an oxidant as an example, if the addition rate is too fast, there will be a serious decomposition problem, resulting in low hydrogen peroxide utilization rate, Fe 2+ May not be completely oxidized to Fe 3+ .
[0056] In the above steps S1 and S2 of the present invention, firstly, the aerobic roasted lithium iron phosphate battery powder is acid-leached to obtain an acid-leaching slurry with a pH of 0 to 0.5, so that the Fe 3+ The method uses excess acid to calcine the LiFePO4 in the lithium iron phosphate battery powder to consume the excess acid in the acid leaching slurry to adjust the pH to 1-2, so that iron and phosphorus are precipitated to obtain lithium liquid and iron phosphate slag. +、Fe 3+ PO4 3+ Converted into free ions, thus ensuring that all Li elements are leached out, and then the pH value is adjusted with LiFePO4 to make Fe 3+ PO4 3+ Re-formation of precipitation, LiFePO4 adjusts the pH value while releasing Li + 、Fe 2+ PO4 3+ To the liquid phase, complete the Li extraction, so as to achieve the recovery and utilization of excess acid in the acid leaching slurry, improve the comprehensive lithium recovery rate, and avoid the increase of by-products by adding additional alkali, greatly reduce the recovery cost and improve economic profits.
[0057] S3: acid-dissolving the ferric phosphate slag and performing solid-liquid separation to obtain graphite slag and ferrophosphorus solution; mixing the ferrophosphorus solution with anhydrous ferric phosphate seed crystals, aging, and obtaining ferric phosphate dihydrate; and calcining the ferric phosphate dihydrate to obtain anhydrous ferric phosphate.
[0058] In some optional embodiments, the ferric phosphate slag can be acid-dissolved using dilute sulfuric acid. The solid-to-liquid ratio of the ferric phosphate slag to the dilute sulfuric acid (taking a concentration of 1.7 mol / L as an example) can be 1 g:3 mL to 1 g:4 mL, such as 1 g:3 mL, 1 g:3.5 mL, or 1 g:4 mL, or other values within the range of 1 g:3 mL to 1 g:4 mL.
[0059] In some optional embodiments, the anhydrous ferric phosphate seed crystals and the ferrophosphorus solution are mixed in a mass ratio of 6:100 to 10:100 (e.g., 6:100, 7:100, 8:100, 9:100, or 10:100, etc.). The aging temperature can be 90° C. to 100° C. (e.g., 90° C., 95° C., or 100° C.), and the aging time can be 4 h to 6 h (e.g., 4 h, 4.5 h, 5 h, 5.5 h, or 6 h, etc.).
[0060] In some optional embodiments, the calcination temperature can be 400° C. to 500° C. (e.g., 400° C., 450° C., or 500° C.), and the calcination time can be 2 hours to 3 hours (e.g., 2 hours, 2.5 hours, or 3 hours). Through the above calcination process, the crystal water in the ferric phosphate dihydrate can be removed to obtain battery-grade ferric phosphate.
[0061] The main component of the phosphorus iron precipitation mother liquor remaining in S3 is dilute sulfuric acid, which can be reused in the reaction process of aerobic roasting of lithium iron phosphate battery powder and acid.
[0062] S4: reacting the lithium solution with alkali and carbonate to precipitate lithium, and separating the solid and liquid to obtain lithium carbonate.
[0063] In some optional embodiments, the acidic lithium solution may be added with alkali to remove impurities and filtered, and the filtrate may be reused to prepare the first intermediate slurry and the second intermediate slurry.
[0064] In some optional embodiments, the alkali may be liquid caustic soda or soda ash, and the carbonate may be sodium carbonate.
[0065] In some optional embodiments, an alkali may be used to adjust the endpoint pH of the lithium solution to no less than 12. The molar ratio of lithium element to carbonate in the lithium solution may be 1:1.05 to 1:1.2, such as 1:1.05, 1:1.1, 1:1.15, or 1:1.2, or other values within the range of 1:1.05 to 1:1.2.
[0066] In some optional embodiments, the lithium deposition temperature is not lower than 80° C., and the lithium deposition time can be 2 h to 3 h (eg, 2 h, 2.5 h, or 3 h, etc.).
[0067] After the lithium precipitation reaction is completed, high-purity lithium carbonate can be obtained by filtering and washing.
[0068] As mentioned above, the method provided by the present invention for recovering lithium and iron phosphate from aerobically roasted lithium iron phosphate batteries effectively recovers lithium, iron, and phosphorus elements with high yields. The entire process is simple, with low acid and alkali consumption and few by-products.
[0069] The features and performance of the present invention are further described in detail below with reference to the embodiments.
[0070] Example 1
[0071] This embodiment provides a method for recovering lithium and iron phosphate from an aerobic roasted lithium iron phosphate battery, comprising the following steps:
[0072] S1: mixing oxygen-calcined lithium iron phosphate battery powder with water to prepare a first intermediate slurry; mixing the first intermediate slurry with acid to obtain an acid leaching slurry with a pH value of 0.24.
[0073] The liquid-solid ratio of water to aerobic-roasted lithium iron phosphate battery powder is 300mL:200g (i.e. 1.5mL:1g). The acid is 3.8mol / L dilute sulfuric acid. The lithium element in the aerobic-roasted lithium iron phosphate battery powder reacts with the H + The first intermediate slurry and the acid were mixed at room temperature and a stirring speed of 300 r / min for 2 hours.
[0074] S2: Mixing oxygen-free roasted lithium iron phosphate battery powder with water to obtain a second intermediate slurry; mixing the acid leaching slurry with the second intermediate slurry to obtain a third intermediate slurry; adding an oxidant to the third intermediate slurry to finally obtain a mixed slurry with a pH value of 1.35; and performing solid-liquid separation on the mixed slurry to obtain iron phosphate slag and lithium liquid.
[0075] The liquid-solid ratio of water to oxygen-free roasted lithium iron phosphate battery powder is 1 mL:1 g. The molar amount of lithium in the oxygen-free roasted lithium iron phosphate battery powder is 0.625 times the total molar amount of iron in the acid leaching slurry. The oxidant is a 30 wt% aqueous solution of hydrogen peroxide. The amount of the oxidant added is to reduce the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder to 0.625 times the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder. 2+ Completely oxidized to Fe 3+ The acid leaching slurry and the second intermediate slurry were mixed at room temperature and a stirring speed of 300 r / min.
[0076] S3: acid-dissolving the ferric phosphate slag and performing solid-liquid separation to obtain graphite slag and ferrophosphorus solution; mixing the ferrophosphorus solution with anhydrous ferric phosphate seed crystals, aging, and obtaining ferric phosphate dihydrate; and calcining the ferric phosphate dihydrate to obtain anhydrous ferric phosphate.
[0077] The acid used was dilute sulfuric acid, and the solid-liquid ratio of ferric phosphate slag to dilute sulfuric acid (concentration: 1.7 mol / L) was 1 g:3 mL. Anhydrous ferric phosphate seed crystals were mixed with the ferrophosphorus solution in a mass ratio of 8:100. The aging temperature was 95°C for 5 hours, and the calcination temperature was 450°C for 2.5 hours.
[0078] S4: reacting the lithium solution with alkali and carbonate to precipitate lithium, and separating the solid and liquid to obtain lithium carbonate.
[0079] The alkali is liquid caustic soda, which is used to adjust the endpoint pH of the lithium solution to 12.5. The carbonate is sodium carbonate, and the molar ratio of lithium to carbonate in the lithium solution is 1:1.1. The lithium precipitation reaction temperature is 85°C, and the reaction time is 2.5 hours.
[0080] Example 2
[0081] This embodiment provides a method for recovering lithium and iron phosphate from an aerobic roasted lithium iron phosphate battery, comprising the following steps:
[0082] S1: mixing oxygen-calcined lithium iron phosphate battery powder with water to prepare a first intermediate slurry; mixing the first intermediate slurry with acid to obtain an acid leaching slurry with a pH value of 0.45.
[0083] The liquid-solid ratio of water to aerobic-roasted lithium iron phosphate battery powder is 300mL:200g (i.e. 1.5mL:1g). The acid is 3.8mol / L dilute sulfuric acid. The lithium element in the aerobic-roasted lithium iron phosphate battery powder reacts with the H + The molar ratio of the first intermediate slurry and the acid was 1:3.15. The first intermediate slurry was mixed with the acid at room temperature and a stirring speed of 250 r / min for 2 hours.
[0084] S2: Mixing oxygen-free roasted lithium iron phosphate battery powder with water to obtain a second intermediate slurry; mixing the acid leaching slurry with the second intermediate slurry to obtain a third intermediate slurry; adding an oxidant to the third intermediate slurry to finally obtain a mixed slurry with a pH value of 1.95; and performing solid-liquid separation on the mixed slurry to obtain iron phosphate slag and lithium liquid.
[0085] The liquid-solid ratio of water to oxygen-free roasted lithium iron phosphate battery powder is 1 mL:1 g. The molar amount of lithium in the oxygen-free roasted lithium iron phosphate battery powder is 0.6 times the total molar amount of iron in the acid leaching slurry. The oxidant is a 30 wt% hydrogen peroxide solution, and the amount of the oxidant added is to reduce the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder to 0.6 times the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder. 2+ Completely oxidized to Fe 3 + The addition rate of the oxidant was 1 mL / min. The acid leaching slurry and the second intermediate slurry were mixed at room temperature and a stirring speed of 250 r / min.
[0086] S3: acid-dissolving the ferric phosphate slag and performing solid-liquid separation to obtain graphite slag and ferrophosphorus solution; mixing the ferrophosphorus solution with anhydrous ferric phosphate seed crystals, aging, and obtaining ferric phosphate dihydrate; and calcining the ferric phosphate dihydrate to obtain anhydrous ferric phosphate.
[0087] The acid used was dilute sulfuric acid, and the solid-liquid ratio of ferric phosphate slag to dilute sulfuric acid (concentration: 1.7 mol / L) was 1 g:3.5 mL. Hydrous ferric phosphate seed crystals and ferric phosphate solution were mixed at a mass ratio of 6:100. The aging temperature was 90°C for 6 hours, and the calcination temperature was 400°C for 3 hours.
[0088] S4: reacting the lithium solution with alkali and carbonate to precipitate lithium, and separating the solid and liquid to obtain lithium carbonate.
[0089] The alkali is liquid caustic soda, which is used to adjust the endpoint pH of the lithium solution to 12. The carbonate is sodium carbonate, and the molar ratio of lithium element to carbonate in the lithium solution is 1:1.05. The lithium precipitation reaction temperature is 80°C, and the lithium precipitation reaction time is 3 hours.
[0090] Example 3
[0091] This embodiment provides a method for recovering lithium and iron phosphate from an aerobic roasted lithium iron phosphate battery, comprising the following steps:
[0092] S1: mixing oxygen-calcined lithium iron phosphate battery powder with water to prepare a first intermediate slurry; mixing the first intermediate slurry with acid to obtain an acid leaching slurry with a pH value of 0.1.
[0093] The liquid-solid ratio of water to aerobic-roasted lithium iron phosphate battery powder is 300mL:200g (i.e. 1.5mL:1g). The acid is 3.8mol / L dilute sulfuric acid. The lithium element in the aerobic-roasted lithium iron phosphate battery powder reacts with the H + The molar ratio of the first intermediate slurry and the acid was 1:3.6. The first intermediate slurry was mixed with the acid at room temperature and a stirring speed of 350 r / min for 2 hours.
[0094] S2: Mixing oxygen-free roasted lithium iron phosphate battery powder with water to obtain a second intermediate slurry; mixing the acid leaching slurry with the second intermediate slurry to obtain a third intermediate slurry; adding an oxidant to the third intermediate slurry to finally obtain a mixed slurry with a pH value of 1; and performing solid-liquid separation on the mixed slurry to obtain iron phosphate slag and lithium liquid.
[0095] The liquid-solid ratio of water to oxygen-free roasted lithium iron phosphate battery powder is 1 mL:1 g. The molar amount of lithium in the oxygen-free roasted lithium iron phosphate battery powder is 0.65 times the total molar amount of iron in the acid leaching slurry. The oxidant is a 30 wt% aqueous solution of hydrogen peroxide. The amount of the oxidant added is to reduce the total Fe content in the acid leaching slurry and the oxygen-free roasted lithium iron phosphate battery powder to 0.65. 2+ Completely oxidized to Fe 3 + The addition rate of the oxidant was 2 mL / min. The acid leaching slurry and the second intermediate slurry were mixed at room temperature and a stirring speed of 350 r / min.
[0096] S3: acid-dissolving the ferric phosphate slag and performing solid-liquid separation to obtain graphite slag and ferrophosphorus solution; mixing the ferrophosphorus solution with anhydrous ferric phosphate seed crystals, aging, and obtaining ferric phosphate dihydrate; and calcining the ferric phosphate dihydrate to obtain anhydrous ferric phosphate.
[0097] The acid used was dilute sulfuric acid, and the solid-liquid ratio of ferric phosphate slag to dilute sulfuric acid (concentration: 1.7 mol / L) was 1 g:4 mL. Hydrous ferric phosphate seed crystals and ferric phosphate solution were mixed at a mass ratio of 10:100. The aging temperature was 99°C for 4 hours, and the calcination temperature was 500°C for 2 hours.
[0098] S4: reacting the lithium solution with alkali and carbonate to precipitate lithium, and separating the solid and liquid to obtain lithium carbonate.
[0099] The alkali was soda ash, and the endpoint pH of the lithium solution was adjusted to 12 using liquid caustic soda. The carbonate was sodium carbonate, and the molar ratio of lithium to carbonate in the lithium solution was 1:1.2. The lithium precipitation reaction temperature was 90°C, and the reaction time was 2 hours.
[0100] Example 4
[0101] The difference between this embodiment and embodiment 1 is that:
[0102] In S1, the oxygen-calcined lithium iron phosphate battery powder is directly mixed with acid to obtain an acid leaching slurry with a pH value of 0.15.
[0103] In S2, the oxygen-free calcined lithium iron phosphate battery powder is directly mixed with the acid leaching slurry and the oxidant to finally obtain a mixed slurry with a pH value of 1.5.
[0104] Comparative Example 1
[0105] The difference between this comparative example and Example 1 is that the pH value of the acid leaching slurry is 5.5.
[0106] Comparative Example 2
[0107] The difference between this comparative example and Example 1 is that the pH value of the mixed slurry is 0.5.
[0108] Comparative Example 3
[0109] The difference between this comparative example and Example 1 is that the pH value of the mixed slurry is 2.5.
[0110] Comparative Example 4
[0111] The difference between this comparative example and Example 1 is that liquid alkali is used instead of oxygen-free roasted lithium iron phosphate battery powder to adjust the pH value of the mixed slurry.
[0112] Results test:
[0113] (1) Three different batches (denoted as batch 1 to batch 3) of aerobically calcined lithium iron phosphate battery powder were weighed and recovered according to the method of Example 1. The content of some elements in the three aerobically calcined lithium iron phosphate battery powders and the anaerobic calcined lithium iron phosphate battery powders are shown in Table 1.
[0114] Table 1
[0115]
[0116] Take 10mL of the acid leaching slurry in step S1 corresponding to each batch of oxygen-roasted lithium iron phosphate battery powder and add Fe 2+ and Fe 3+ The results of the content test are shown in Table 2.
[0117] Table 2
[0118] project <![CDATA[Fe 3+ -g / L]]> <![CDATA[Fe 2+ -g / L]]> Batch 1 65.3638 15.8773 Batch 2 67.6255 14.9726 Batch 3 69.7515 45.8677
[0119] The data such as the amount of anaerobic roasted battery powder used in step S2, the total liquid volume of lithium solution, the concentration of some elements, the pH value and the lithium leaching rate corresponding to each batch of aerobic roasted lithium iron phosphate battery powder were compared respectively. Among them, the lithium leaching rate = total liquid volume × lithium content in lithium solution / (amount of aerobic roasted battery powder used × lithium content of aerobic roasted battery powder + amount of anaerobic roasted battery powder used × lithium content of anaerobic roasted battery powder). The results are shown in Table 3.
[0120] Table 3
[0121]
[0122] As can be seen from Table 3, the lithium leaching rates of the three batches of aerobic roasted lithium iron phosphate battery powder obtained by the method provided in Example 1 all reached above 99%.
[0123] (2) Seven different batches (denoted as batches 4 to 10) of aerobically calcined lithium iron phosphate battery powder were weighed and recovered according to the methods of Examples 2 to 4 and Comparative Examples 1 to 4. The contents of some elements in the seven aerobically calcined lithium iron phosphate battery powders and the oxygen-free calcined lithium iron phosphate battery powders are shown in Table 4.
[0124] Table 4
[0125]
[0126] Take 10mL of the acid leaching slurry in step S1 corresponding to each batch of oxygen-roasted lithium iron phosphate battery powder and add Fe 2+ and Fe 3+ The results of the content test are shown in Table 5.
[0127] Table 5
[0128] project <![CDATA[Fe 3+ -g / L]]> <![CDATA[Fe 2+ -g / L <!-- 8 -->]]> Batch 4 65.0521 17.4121 Batch 5 69.7554 21.1920 Batch 6 92.4372 38.4589 Batch 7 0.0504 0.0496 Batch 8 65.5831 15.3443 Batch 9 67.8092 26.5145 Batch 10 67.7014 20.3023
[0129] The data such as the amount of anaerobic roasted battery powder used in step S2, the total liquid volume of lithium solution, the concentration of some elements, the pH value, and the lithium leaching rate corresponding to each batch of aerobic roasted lithium iron phosphate battery powder were compared respectively. Among them, the lithium leaching rate = total liquid volume × lithium content in lithium solution / (amount of aerobic roasted battery powder used × lithium content of aerobic roasted battery powder + amount of anaerobic roasted battery powder used × lithium content of anaerobic roasted battery powder). The results are shown in Table 6.
[0130] Table 6
[0131]
[0132]
[0133] The above results show that the lithium leaching rates obtained by the methods provided in Examples 2 to 4 all reached over 99%, while the lithium leaching rates obtained by the methods provided in Comparative Examples 1 to 4 all failed to reach 99%. In other words, the methods provided in the embodiments of the present invention can effectively improve the lithium leaching rate.
[0134] In summary, the method for recovering lithium and iron phosphate from aerobic roasted lithium iron phosphate batteries provided by the present invention firstly acid-leaches the aerobic roasted lithium iron phosphate battery powder to obtain an acid-leaching slurry with a pH of 0 to 0.5, so that the Fe 3+ The method uses excess acid to calcine the LiFePO4 in the lithium iron phosphate battery powder to consume the excess acid in the acid leaching slurry to adjust the pH to 1-2, so that iron and phosphorus are precipitated to obtain lithium liquid and iron phosphate slag. + 、Fe 3+ PO4 3+ Converted into free ions, thus ensuring that all Li elements are leached out, and then the pH value is adjusted with LiFePO4 to make Fe 3+ PO4 3+ Re-formation of precipitation, LiFePO4 adjusts the pH value while releasing Li + 、Fe 2+ PO4 3+ To the liquid phase, complete the Li extraction, so as to achieve the recovery and utilization of excess acid in the acid leaching slurry, improve the comprehensive lithium recovery rate, and avoid the increase of by-products by adding additional alkali, greatly reduce the recovery cost and improve economic profits.
[0135] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.
Claims
1. A method for recovering lithium and iron phosphate from an aerobic roasted lithium iron phosphate battery, characterized in that: The following steps are involved: The oxygen-roasted lithium iron phosphate battery powder is reacted with acid to obtain an acid leaching slurry with a pH value of 0 to 0.5; Mixing the acid leaching slurry with oxygen-free roasted lithium iron phosphate battery powder and an oxidant to obtain a mixed slurry with a pH value of 1 to 2; performing solid-liquid separation on the mixed slurry to obtain iron phosphate slag and lithium liquid; The ferric phosphate slag is acid-dissolved and solid-liquid separated to obtain graphite slag and ferrophosphorus solution; the ferrophosphorus solution is mixed with anhydrous ferric phosphate seed crystals and aged to obtain ferric phosphate dihydrate; the ferric phosphate dihydrate is calcined to obtain anhydrous ferric phosphate; The lithium solution is reacted with alkali and carbonate to precipitate lithium, and the solid-liquid is separated to obtain lithium carbonate.
2. The method according to claim 1, characterized in that The lithium element in the oxygen-calcined lithium iron phosphate battery powder and the H + The molar ratio is 1:3.15 to 1:3.
6.
3. The method according to claim 1, characterized in that First, the oxygen-roasted lithium iron phosphate battery powder is mixed with water to prepare a first intermediate slurry; then the first intermediate slurry is mixed with the acid to obtain an acid leaching slurry; Preferably, the liquid-to-solid ratio of the water to the aerobic-roasted lithium iron phosphate battery powder is 1 mL:1 g to 2 mL:1 g.
4. The method according to claim 1, wherein The molar amount of lithium element in the oxygen-free calcined lithium iron phosphate battery powder is 0.6 to 0.65 times the total molar amount of iron element in the acid leaching slurry.
5. The method according to claim 1, wherein The amount of the oxidant added is to reduce the total Fe 2+ Completely oxidized to Fe 3+ 1.2 to 1.5 times the theoretical amount required.
6. The method according to claim 5, characterized in that The oxidant comprises at least one of hydrogen peroxide, ozone and sulfur dioxide; Preferably, the oxidizing agent is hydrogen peroxide.
7. The method according to claim 1, characterized in that Mixing the oxygen-free roasted lithium iron phosphate battery powder with water to obtain a second intermediate slurry; mixing the acid leaching slurry with the second intermediate slurry to obtain a third intermediate slurry; adding the oxidant to the third intermediate slurry to obtain the mixed slurry; Preferably, the liquid-to-solid ratio of the water to the oxygen-free calcined lithium iron phosphate battery powder is 1 mL:1 g to 2 mL:1 g; Preferably, the addition rate of the oxidant is 1 mL / min to 2 mL / min.
8. The method according to claim 1, characterized in that The aging temperature is 90° C. to 100° C., and the aging time is 4 h to 6 h.
9. The method according to claim 1, characterized in that The calcination temperature is 400° C. to 500° C., and the calcination time is 2 h to 3 h.
10. The method according to claim 1, characterized in that The temperature of the lithium precipitation reaction is not lower than 80° C., and the time is 2 h to 3 h.