Recycling method of waste lithium iron phosphate
By using aqueous citric acid solution and specific catalysts to sonicate waste lithium iron phosphate, the problems of high energy consumption and high carbon emissions of existing recycling methods are solved, and efficient and environmentally friendly metal recycling effects are achieved.
Patent Information
- Application Number
- CN202411902772.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-03-28
AI Technical Summary
The existing lithium-ion battery waste recycling methods have problems with high energy consumption and high carbon emissions, and the hydrometallurgy method uses a large number of high concentrations of acids and reagents to cause secondary pollution.
Use aqueous citric acid solution and specific catalysts (such as polycarbonate, polyethylene terephthalate, etc.) to ultrasonicate waste lithium iron phosphate to achieve efficient leaching and recycling of metals.
The leaching efficiency of metals is improved at lower acid concentrations, energy consumption and carbon emissions are reduced, secondary pollution is avoided, and the properties of the catalyst remain unchanged after repeated use, which is stable and economical.
Abstract
Description
Technical Field
[0001] The invention relates to a method for recovering waste lithium iron phosphate and belongs to the technical field of lithium material recovery. Background Art
[0002] Lithium-ion batteries (LIBs) are widely used in various electronic devices and electric vehicles. In recent years, the scale of use has also increased year by year. However, due to lifespan limitations, the number of discarded lithium-ion batteries has also continued to increase, becoming a huge source of pollution that may seriously threaten the environment and public health. On the other hand, discarded lithium-ion batteries contain abundant metal elements, which are much higher than the content in upstream raw material minerals. Therefore, recycling the metal elements in the cathode of used lithium batteries has great environmental, social and economic significance.
[0003] Lithium iron phosphate (LiFePO4) has become one of the most popular cathodes due to its low cost, high safety and good stability. The recovery methods of industrial waste LiFePO4 are mainly divided into two types: pyrometallurgy and hydrometallurgy. Pyrometallurgy has high energy consumption and will lead to volatilization of lithium and high carbon emissions. In contrast, hydrometallurgical methods are more widely used to recover metals from waste LiFePO4. Hydrometallurgy mainly uses inorganic acid leaching processes such as H2SO4 and H3PO4, while adding redox agents to promote leaching efficiency, and then separates and purifies with appropriate reagents. Although this method has a high lithium ion leaching rate, the use of large amounts of high-concentration acids and reagents can also cause secondary pollution. Summary of the invention
[0004] The object of the present invention is a method for recovering waste lithium iron phosphate.
[0005] To achieve the purpose of the present invention, the method comprises:
[0006] A. uniformly mixing the citric acid aqueous solution, the catalyst and the waste lithium iron phosphate to obtain a suspension;
[0007] B. treating the suspension with ultrasound for 1 to 24 hours, stopping ultrasound and allowing to stand for 0.5 to 2 hours;
[0008] C. After standing, scrape off the catalyst solid floating on the top of the solution, and filter the remaining solution to obtain FePO4 filter residue and clarified lithium-containing leachate;
[0009] The catalyst is at least one of polycarbonate, polyethylene terephthalate, nitrile rubber and polyamide plastic powder.
[0010] In a specific embodiment, the concentration of waste lithium iron phosphate in the suspension in step A is 5 to 20 g / L.
[0011] In a specific embodiment, the amount of the catalyst in step A is 10% to 30% of the mass of the waste lithium iron phosphate.
[0012] Preferably, the mixing method in step A is to first mix the citric acid aqueous solution and the catalyst evenly, and then add the waste lithium iron phosphate and mix evenly. The catalyst can be directly mixed with citric acid (solid particles) in water because citric acid is a substance that is easily soluble in water. However, some catalysts have strong adsorption capacity, and directly mixing with waste lithium iron phosphate may be detrimental to the dispersion of the catalyst in the citric acid solution, so it is best to mix in a preferred order.
[0013] In a specific embodiment, the concentration of the citric acid solution is 0.2-2 mol / L.
[0014] In a specific embodiment, the powder has a particle size of 10 to 200 μm.
[0015] In a specific embodiment, the power of the ultrasound is 120-300W.
[0016] In a specific embodiment, the frequency of the ultrasound is 30 to 50 Hz.
[0017] Preferably, the temperature of the ultrasound is 25-80°C.
[0018] In a specific embodiment, the catalyst solid in step C is dried and then returned to step A for reuse.
[0019] In a specific embodiment, the method further comprises: washing and drying the FePO4 filter residue to obtain a FePO4 product.
[0020] The clarified lithium-containing leachate also contains Fe, which needs further treatment to separate Li and Fe. The existing method of precipitating and separating Li and Fe from the lithium-rich leachate can be used. In a specific embodiment, the method also includes: adjusting the pH of the lithium-containing leachate to 9-10, stirring, precipitating Fe(OH)3, filtering to obtain a Li-rich solution; reacting the Li-rich solution with a carbonate to obtain a Li2CO3 precipitate; the carbonate is at least one of Na2CO3 and K2CO3.
[0021] In a specific embodiment, the stirring time is 10 to 60 minutes, and the stirring speed is 50 to 300 rpm.
[0022] In a specific embodiment, the Li-rich solution is heated to 40-90° C. to react with carbonate.
[0023] Beneficial effects:
[0024] (1) The present invention is based on the contact electrocatalysis (CEC) principle, uses PC, PET, NBR, and PA powders as catalysts, and leaches and recovers waste lithium iron phosphate under ultrasonic conditions. Compared with conventional high-concentration organic acid leaching, the present invention can improve the leaching efficiency of conventional organic acids for metals at lower acid concentrations without adding redox reagents, thereby improving the metal recovery rate;
[0025] (2) The PC, PET, NBR, and PA powders of the present invention are used as catalysts, and their properties do not change significantly after repeated use. Compared with conventional catalysts, this type of catalyst has a wide source, is simple to prepare, has more stable performance, and is easy to recycle and reuse;
[0026] (3) The present invention uses citric acid solution to leach and recover the waste lithium iron phosphate positive electrode material. Compared with the current conventional strong acid (H2SO4, etc.) + oxidant (H2O2, etc.) leaching, the present invention firstly uses organic acids that are easy to decompose and secondly does not require the addition of additional redox reagents, so it is economical and environmentally friendly. DETAILED DESCRIPTION
[0027] To achieve the purpose of the present invention, the method comprises:
[0028] A. uniformly mixing the citric acid aqueous solution, the catalyst and the waste lithium iron phosphate to obtain a suspension;
[0029] B. treating the suspension with ultrasound for 1 to 24 hours, stopping ultrasound and allowing to stand for 0.5 to 2 hours;
[0030] C. After standing, scrape off the catalyst solid floating on the top of the solution, and filter the remaining solution to obtain FePO4 filter residue and clarified lithium-containing leaching solution;
[0031] The catalyst is at least one of polycarbonate, polyethylene terephthalate, nitrile rubber and polyamide plastic powder.
[0032] In a specific embodiment, the concentration of waste lithium iron phosphate in the suspension in step A is 5 to 20 g / L.
[0033] In a specific embodiment, the amount of the catalyst in step A is 10% to 30% of the mass of the waste lithium iron phosphate.
[0034] Preferably, the mixing method in step A is to first mix the citric acid aqueous solution and the catalyst evenly, and then add the waste lithium iron phosphate and mix evenly. The catalyst can be directly mixed with citric acid (solid particles) in water because citric acid is a substance that is easily soluble in water. However, some catalysts have strong adsorption capacity, and directly mixing with waste lithium iron phosphate may be detrimental to the dispersion of the catalyst in the citric acid solution, so it is best to mix in a preferred order.
[0035] In a specific embodiment, the concentration of the citric acid solution is 0.2-2 mol / L.
[0036] In a specific embodiment, the powder has a particle size of 10 to 200 μm.
[0037] In a specific embodiment, the power of the ultrasound is 120-300W.
[0038] In a specific embodiment, the frequency of the ultrasound is 30 to 50 Hz.
[0039] Preferably, the temperature of the ultrasound is 25-80°C.
[0040] In one specific embodiment, the catalyst solid in step C is dried and then returned to step A for reuse.
[0041] In a specific embodiment, the method further comprises: washing and drying the FePO4 filter residue to obtain a FePO4 product.
[0042] The clarified lithium-containing leachate also contains Fe, which needs further treatment to achieve the separation of Li and Fe. The existing method of precipitating and separating Li and Fe from the lithium-rich leachate can be used.
[0043] In a specific embodiment, the method further includes: adjusting the pH of the lithium-containing leaching solution to 9-10, stirring, precipitating Fe(OH)3, and filtering to obtain a Li-rich solution; reacting the Li-rich solution with a carbonate to obtain a Li2CO3 precipitate; the carbonate is at least one of Na2CO3 and K2CO3.
[0044] In a specific embodiment, the stirring time is 10 to 60 minutes, and the stirring speed is 50 to 300 rpm.
[0045] In a specific embodiment, the Li-rich solution is heated to 40-90° C. to react with carbonate.
[0046] The specific implementation modes of the present invention are further described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.
[0047] Example 1
[0048] Weigh 1.68g of citric acid solid and add it to 40mL of ultrapure water, stir until completely dissolved to obtain a 0.2mol / L citric acid solution; weigh 80mg of PA66 powder with a particle size of 10-100μm and a D50 of 20μm, add it to the citric acid solution, and stir it magnetically for 1h; continue to add 400mg of waste lithium iron phosphate powder, and then place the container in an ultrasonic cleaning machine, set the temperature to 80℃, the ultrasonic power to 200w, the frequency to 40KHz, and perform ultrasonic treatment for 6h;
[0049] After the ultrasonic treatment, the mixture was allowed to stand for 1 hour, and the floating matter was scraped off with a scraper. The remaining turbid liquid was then filtered, and the residue was washed with ultrapure water for 3 times, and vacuum dried at 110°C for 12 hours to obtain the recovered FePO4 product. A small amount of the filtrate was taken and the concentrations of Li and Fe elements were determined by ICP-OES, and the leaching rates were calculated to be 95.3% for Li and 3.2% for Fe, respectively. The floating matter was scraped off with a scraper, washed with pure water for more than 3 times, and dried at 60-80°C to obtain the recovered catalyst.
[0050] NaOH solution was added to the remaining filtrate to adjust the pH to 9-10, and the mixture was slowly stirred for 20 minutes. The precipitate was removed by filtration to obtain a clear filtrate. The filtrate was heated to 90°C, 135 mg of Na2CO3 particles was slowly added, and the mixture was slowly stirred until the precipitate was completely precipitated. The Li2CO3 precipitate was filtered out and washed with boiling ultrapure water for 3 times. The mixture was vacuum dried at 110°C for 12 hours to obtain a recovered Li2CO3 product.
[0051] Example 2
[0052] Weigh 10.08g of citric acid solid and add it to 120mL of ultrapure water, stir until completely dissolved, and obtain 0.4mol / L citric acid solution; weigh 240mg of PET powder with a D50 of 40μm, add it to the citric acid solution, and stir it magnetically for 1h; continue to add 1400mg of waste lithium iron phosphate powder, and then place the container in an ultrasonic cleaning machine, set the temperature to 40℃, the ultrasonic power to 200w, the frequency to 40KHz, and ultrasonically treat for 6h. After the ultrasonic treatment is completed, let it stand for 0.5h, scrape off the catalyst solid floating on the top of the solution, and then filter the remaining turbid liquid, take a small amount of clarified filtrate and use ICP-OES to determine the concentration of Li and Fe elements, and calculate the leaching rates of Li 92.4% and Fe 5.5%, respectively.
[0053] Example 3
[0054] Weigh 16.8g of citric acid solid and add it to 80mL of ultrapure water, stir until completely dissolved to obtain a 1mol / L citric acid solution; weigh 160mg of NBR powder with a D50 of 100μm, add it to the citric acid solution, and stir it magnetically for 2h; continue to add 800mg of waste lithium iron phosphate powder, and then place the container in an ultrasonic cleaning machine, set the temperature to 30℃, the ultrasonic power to 180w, the frequency to 40KHz, and ultrasonically treat for 10h. After the ultrasonic treatment is completed, let it stand for 1h, scrape off the catalyst solid floating on the top of the solution, and then filter the remaining turbid liquid, take a small amount of clarified filtrate and use ICP-OES to determine the concentration of Li and Fe elements, and calculate the leaching rates of Li 90.6% and Fe 6.9%, respectively.
[0055] Example 4
[0056] Weigh 1.68g of citric acid solid and add it to 40mL of ultrapure water, stir until completely dissolved, and obtain a 0.2mol / L citric acid solution; weigh 120mg of PC powder with a D50 of 50μm, add it to the citric acid solution, and stir it magnetically for 1h; continue to add 400mg of waste lithium iron phosphate powder, and then place the container in an ultrasonic cleaning machine, set the temperature to 30℃, the ultrasonic power to 200w, the frequency to 40KHz, and ultrasonically treat for 8h. After the ultrasonic treatment is completed, let it stand for 2h, scrape off the catalyst solid floating on the top of the solution, and then filter the remaining turbid liquid, take a small amount of clarified filtrate and use ICP-OES to determine the concentration of Li and Fe elements, and calculate the leaching rates of Li 93.7% and Fe 4.8%, respectively.
[0057] Comparative Example 1
[0058] Weigh 1.68g of citric acid solid and add it to 40mL of ultrapure water, stir until completely dissolved to obtain a 0.2mol / L citric acid solution; add 400mg of waste lithium iron phosphate powder, then place the container in an ultrasonic cleaning machine, set the temperature to 30℃, ultrasonic power to 200w, frequency to 40KHz, and ultrasonic treatment for 6h. After the ultrasonic treatment, filter the turbid liquid, take a small amount of filtrate and use ICP-OES to determine the concentration of Li and Fe elements, and calculate the leaching rates of Li 80.1% and Fe 91%, respectively.
[0059] Comparative Example 2
[0060] Weigh 4.2g of citric acid solid and add it to 40mL of ultrapure water, stir until completely dissolved to obtain a 0.25mol / L citric acid solution; add 400mg of waste lithium iron phosphate powder, then place the container in an ultrasonic cleaning machine, set the temperature to 60℃, ultrasonic power to 200w, frequency to 40KHz, and ultrasonic treatment for 8h. After the ultrasonic treatment, filter the turbid liquid, take a small amount of clarified filtrate and use ICP-OES to determine the concentration of Li and Fe elements, and calculate the leaching rates of Li 83.6% and Fe 92.3%, respectively.
[0061] Comparative Example 3
[0062] Weigh 1.68g of citric acid solid and add it to 40mL of ultrapure water, stir until completely dissolved, and obtain 0.2mol / L citric acid solution; weigh 80mg of SiO2 powder with a D50 of 2μm, add it to the citric acid solution, and stir it magnetically for 1h; add 400mg of waste lithium iron phosphate powder, and then place the container in an ultrasonic cleaning machine, set the temperature to 30℃, the ultrasonic power to 200w, the frequency to 40KHz, and ultrasonically treat for 6h. After the ultrasonic treatment, filter the turbid liquid, take a small amount of filtrate and use ICP-OES to determine the concentration of Li and Fe elements, and calculate the leaching rates of Li 68.2% and Fe 88.4%, respectively.
Claims
1. A method for recovering waste lithium iron phosphate, characterized in that: The method comprises: A. uniformly mixing the citric acid aqueous solution, the catalyst and the waste lithium iron phosphate to obtain a suspension; B. treating the suspension with ultrasound for 1 to 24 hours, stopping ultrasound and allowing to stand for 0.5 to 2 hours; C. After standing, scrape off the catalyst solid floating on the top of the solution, and filter the remaining solution to obtain FePO4 filter residue and clarified lithium-containing leachate; The catalyst is at least one of polycarbonate, polyethylene terephthalate, nitrile rubber and polyamide plastic powder.
2. The method for recovering waste lithium iron phosphate according to claim 1, characterized in that: The concentration of waste lithium iron phosphate in the suspension in step A is 5 to 20 g / L.
3. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The amount of the catalyst used in step A is 10% to 30% of the mass of the waste lithium iron phosphate.
4. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The mixing method in step A is to first mix the citric acid aqueous solution and the catalyst evenly, and then add the waste lithium iron phosphate and mix evenly.
5. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The concentration of the citric acid solution is 0.2-2 mol / L.
6. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The particle size of the powder is 10 to 200 μm.
7. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The power of the ultrasound is 120-300W.
8. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The frequency of the ultrasound is 30-50 Hz.
9. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The temperature of the ultrasound is 25-80°C.
10. The method for recovering waste lithium iron phosphate according to claim 1 or 2, characterized in that: The catalyst solid in step C is dried and returned to step A for reuse.