A method for recovering high-purity cobalt sulfate from waste lithium-ion batteries

Abstract

The present application relates to the technical field of solid waste waste battery recycling, and discloses a method for recovering high-purity cobalt sulfate from waste lithium ion batteries, which comprises the following steps: waste lithium ion battery pretreatment, acid leaching treatment, leaching liquid pretreatment, manganese precipitation treatment, cobalt sulfate recovery, nickel recovery, and lithium recovery process, and achieves the goal of recovering high-purity cobalt sulfate from waste lithium ion batteries, and also achieves the graded recovery of manganese, nickel and lithium, so that the method conforms to the green environmental protection and sustainable development concept, and has good economic benefits.

Description

Technical Field

[0001] This invention relates to the field of solid waste and used battery recycling technology, specifically a method for recovering high-purity cobalt sulfate from used lithium-ion batteries. Background Technology

[0002] In the 1990s, lithium-ion batteries officially entered the commercial development stage. Due to their many advantages, such as high energy density, high operating voltage, long cycle life, no memory effect, and good safety, they are widely used in mobile electronic devices, aerospace, medical and other fields. In recent years, with the steady increase in market demand for lithium-ion batteries, my country's lithium-ion battery production has increased year by year. At the same time, the number of waste lithium-ion batteries is also increasing. Lithium-ion batteries are generally composed of positive electrode, negative electrode, electrolyte and separator. Waste lithium-ion batteries contain a large number of metals. Valuable metals such as cobalt, lithium, and nickel in the positive electrode material have important recycling value. Recycling these metals is beneficial to alleviating environmental pollution and natural resource shortages.

[0003] For example, Chinese patent application CN107742760A discloses a method for extracting lithium from waste lithium-ion batteries, which realizes the recovery of lithium from waste lithium-ion batteries. However, Chinese patent application CN107742760A only realizes the recovery of one metal and fails to simultaneously recover multiple metals. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for recovering high-purity cobalt sulfate from spent lithium-ion batteries, comprising the following steps: Step 1: Pretreatment of waste lithium-ion batteries: The waste lithium-ion batteries are pretreated to obtain cathode active materials and alumina adsorbent. Step 2, Acid Leaching Treatment: The rice husk powder is hydrolyzed with sulfuric acid to obtain rice husk hydrolysate; the rice husk hydrolysate, the cathode active material obtained after pretreatment of waste lithium-ion batteries, and the sulfuric acid aqueous solution are mixed and acid leached to obtain leachate and leachate residue. Step 3: Leachate pretreatment: After the leachate undergoes an adsorption treatment with alumina adsorbent, the pH is adjusted and a precipitation treatment is performed to obtain the pretreated leachate. Step 4: Precipitation treatment of manganese: Add potassium permanganate to the pretreated leachate for secondary precipitation treatment to obtain manganese dioxide precipitate and primary leachate; Step 5, Cobalt sulfate recovery: Add silica-based adsorbent to the primary leachate for secondary adsorption treatment to obtain cobalt-containing filter residue and secondary leachate; use the cobalt-containing filter residue as raw material to prepare high-purity cobalt sulfate; The preparation method of the silica adsorbent includes the following steps: Step S1: Prepare mesoporous nano-silica; Modify the mesoporous nano-silica with 3-mercaptopropyltrimethoxysilane to obtain modified mesoporous nano-silica. Step S2: Modified mesoporous nano-silica reacts with methacryloyloxyethyltrimethylammonium chloride to obtain a silica-based adsorbent; Step 6, Nickel Recovery: Extract nickel from the secondary leaching solution to obtain a lithium-rich solution and a nickel-rich solution. The nickel-rich solution is then post-treated to obtain nickel sulfate. Step 7, Lithium Recovery: Add sodium carbonate to the lithium-rich solution and react to obtain lithium carbonate.

[0005] Preferably, in step one, the method for pretreating waste lithium-ion batteries includes the following steps: First, positive electrode sheets are obtained by dismantling used lithium-ion batteries; The positive electrode sheet is cut and then heated to 500-520℃ in air at a heating rate of 5℃ / min for 1.5-2.5h. After that, it is passed through a 400-500 mesh sieve to obtain the cathode active material and the sieved aluminum foil. The sieved aluminum foil is washed with deionized water 3-5 times to obtain clean aluminum foil and washing liquid. The washing liquid is combined, filtered, and dried to obtain aluminum foil fragments. Aluminum foil fragments and 0.5 mol / L sodium hydroxide aqueous solution were mixed at a mass ratio of (2-3):(150-250), stirred at 68-72℃ for 2-4 h, cooled, and filtered. The pH of the filtrate was adjusted to 5.9-6.1 at 68-72℃, filtered, and the resulting white precipitate was collected, washed, and dried to obtain a white precursor. The white precursor was then heated to 500-700℃ at a heating rate of 5℃ / min in air atmosphere and calcined for 1.5-2.5 h to obtain alumina adsorbent. In the above process, based on the density and particle size difference between the cathode active material and the aluminum foil, the cathode active material and the aluminum foil are separated. The finer cathode active material passes through a screen, while the aluminum foil remains on the screen, resulting in cathode active material and sieved aluminum foil. The sieved aluminum foil is then treated with a washing solution obtained by rinsing with deionized water to obtain aluminum foil fragments. Next, the aluminum foil fragments are first treated with alkali to remove the remaining cathode active material, and then treated with alkali again to remove the residual cathode material. Subsequently, the fragments are calcined to produce a porous alumina adsorbent with a high specific area. The alumina adsorbent can efficiently remove fluorides from the leaching solution of the cathode active material.

[0006] Preferably, in step two, the acid leaching treatment method is as follows: After washing and drying, rice husks are ground for 5-10 minutes to obtain rice husk powder with a particle size of 60-120 μm. The rice husk powder is added to a 9.2 mol / L sulfuric acid aqueous solution with a solid-liquid mass ratio of (4.5-5.5):1. The mixture is stirred at 58-62℃ and hydrolyzed for 40-80 minutes. Then, the pH of the system is adjusted to 1-2 with sodium hydroxide to obtain rice husk hydrolysate. The rice husk hydrolysate was mixed with distilled water, stirred, and heated to 50-60℃. Then, the cathode active material was added, and the pH was adjusted to 1-2 with a 50wt% sulfuric acid aqueous solution. The mixture was then acid-leached for 6-8 hours. After the reaction was completed, the mixture was filtered to obtain the leachate and the leachate residue. The mass ratio of the rice husk hydrolysate, distilled water, and cathode active material was (40-60):(240-260):(12-15). In the above process, rice husks contain macromolecular polysaccharides such as cellulose, hemicellulose, and lignin. Rice husk hydrolysis can generate soluble small molecule organic compounds such as glucose and sucrose. These hydrolysis products exist in aqueous solution in a partially unbranched form, and their free aldehyde groups (-CHO) are easily oxidized to carboxyl groups, thus exhibiting reducing properties. When the cathode active material comes into contact with the rice husk hydrolysate, these reducing hydrolysate products will convert the high-valence key metals into low-valence states. All high-valence metals can be reduced to +2 valence. In a dilute acid system, these low-valence key metals are easily leached, with leaching rates of Li, Ni, Co, and Mn all exceeding 98%, thus achieving efficient recovery. In addition, compared with the acidity required by traditional hydrometallurgical leaching processes (3-6 mol / L), the acidity required for leaching electrode materials treated with rice husk hydrolysate is reduced by tens of times. This will reduce the input of raw materials during acid leaching and reduce the risk of equipment corrosion.

[0007] Preferably, in step three, the method for pretreating the leachate is as follows: Add the alumina adsorbent to the leachate with a solid-liquid ratio of 30-40 g / L, adjust the pH to 2.8-3 with 0.1 mol / L sodium hydroxide aqueous solution, perform an adsorption treatment at 30-40℃ for 70-90 min, filter, and obtain the adsorbed leachate. The pH of the adsorption-treated leachate was adjusted to 4.4-4.6, and a precipitation treatment was performed for 40-60 minutes. The leachate was then filtered to remove the filter residue, and the pretreated leachate was obtained. In the above process, alumina adsorbent is first added to the leachate to remove fluoride compounds. On the one hand, fluorides in the leachate form metal fluoride precipitates, reducing metal recovery efficiency and product purity, and the resulting fluoride-containing wastewater and solid waste are harmful to the environment. Furthermore, by adjusting the pH of the system to 4.4-4.6, iron and aluminum impurities are removed. Therefore, by pretreating the leachate, fluoride compounds, iron, and aluminum impurities can be removed, which helps to improve the purity and recovery rate of the product.

[0008] Preferably, in step four, the method for precipitating manganese is as follows: At 24-26℃, potassium permanganate was added to the pretreated leachate to make the concentration of potassium permanganate 0.007-0.009 g / mL. The pH was adjusted to 1.8-2 with 0.1 mol / L sulfuric acid aqueous solution. A secondary precipitation treatment was carried out for 20-30 min. After filtration, manganese dioxide precipitate and primary leachate were obtained. In the above process, potassium permanganate is added to the pretreated leachate. Through the oxidation properties of potassium permanganate, the manganese ions in the system are selectively oxidized into manganese dioxide precipitate, thereby separating the manganese ions from the pretreated leachate.

[0009] Preferably, in step five, the method for recovering cobalt sulfate is as follows: A silica-based adsorbent was added to the primary leachate at a solid-liquid ratio of 30-40 g / L. Then, sodium nitrite and nitric acid were added to make the sodium nitrite concentration 0.5-1 mol / L and the H+ concentration 0.021-0.025 mol / L. A secondary adsorption treatment was then carried out at 35-45℃ for 4-5 hours. After filtration, cobalt-containing filter residue and secondary leachate were obtained. The cobalt-containing filter residue washed with deionized water was added to a 1-1.5 mol / L HCl aqueous solution with a solid-liquid ratio of 25-35 g / L. The solution was desorbed at 24-28℃ for 1.5-2.5 h, and then filtered to obtain a cobalt-rich solution and the recovered silica-based adsorbent. At 24-28℃, 25-28wt% ammonia was added to the cobalt-rich solution until no precipitate was formed. The solution was filtered, and the resulting solid product was washed with deionized water and ethanol and then dried to obtain cobalt hydroxide. In a nitrogen atmosphere, at 24-28℃, cobalt hydroxide was mixed with a 1 mol / L sulfuric acid aqueous solution, and the molar ratio of cobalt hydroxide to sulfuric acid was controlled at 1:1. The mixture was stirred for 30-60 min. After the reaction was completed, the mixture was evaporated, concentrated, cooled and crystallized to obtain high-purity cobalt sulfate. In the above process, in the sodium nitrite medium, nitrite ions can complex with cobalt ions but have poor binding ability with other metals. Therefore, it is possible to selectively separate cobalt ions from a system containing Li(I), Co(II), and Ni(II). The complex formed by nitrite ions and cobalt ions undergoes ion exchange with chloride ions in the silica-based adsorbent, thereby adsorbing cobalt ions onto the silica-based adsorbent. Subsequently, the cobalt ion complex can be rapidly desorbed in an HCl aqueous solution, releasing the cobalt ions into the solution, resulting in a cobalt-rich solution and the recovered silica-based adsorbent. The recovered silica-based adsorbent can be repeatedly recycled for the selective adsorption of cobalt ions. Therefore, the silica-based adsorbent of the present invention has the advantages of high adsorption efficiency, good selectivity, and recyclability. Further, ammonia water is added to the cobalt-rich solution to precipitate cobalt ions, obtaining cobalt hydroxide. Cobalt hydroxide reacts with sulfuric acid, and then is evaporated, concentrated, cooled, and crystallized to obtain high-purity cobalt sulfate.

[0010] Preferably, in step five, the preparation method of the silica-based adsorbent is as follows: Step S1: Add mesoporous nano-silica to ethanol, sonicate, then add 3-mercaptopropyltrimethoxysilane, and stir for 8-12 hours. After the reaction is complete, centrifuge, wash, and dry to obtain modified mesoporous nano-silica; wherein, the mass ratio of the mesoporous nano-silica, ethanol, and 3-mercaptopropyltrimethoxysilane is (0.1-0.2):(320-640):(0.8-1.2); Step S2: Add modified mesoporous nano-silica to ethanol, ultrasonically heat to 65-75℃, then add methacryloyloxyethyltrimethylammonium chloride and azobisisobutyronitrile, stir and react for 4-6 hours. After the reaction is completed, filter, wash and dry to obtain silica-based adsorbent; wherein, the mass ratio of modified mesoporous nano-silica, ethanol, methacryloyloxyethyltrimethylammonium chloride and azobisisobutyronitrile is (0.1-0.2):(320-640):(1.2-2.6):(0.02-0.04); In the above process, thiol groups were introduced into the mesoporous nano-silica by modifying it with 3-mercaptopropyltrimethoxysilane, resulting in modified mesoporous nano-silica. The thiol groups in the modified mesoporous nano-silica reacted with the carbon-carbon double bonds of methacryloyloxyethyltrimethylammonium chloride, covalently grafting methacryloyloxyethyltrimethylammonium chloride onto the mesoporous nano-silica. This solved the problems of low loading rate and easy desorption of methacryloyloxyethyltrimethylammonium chloride on the mesoporous nano-silica, thereby improving the adsorption and recovery effect of cobalt ions.

[0011] Preferably, the method for preparing the mesoporous nano-silica is as follows: Octane was dispersed in deionized water and stirred at 65-75°C for 20-40 min. Then, hexadecyltrimethylammonium bromide was added and stirred at 65-75°C for 4-6 min. Next, styrene, 2,2'-azo(2-methylpropylamidine) dihydrochloride, L-lysine, and tetraethyl silicate were added sequentially, and the mixture was stirred for 3.5-4.5 h. After the reaction was complete, the mixture was centrifuged, washed, dried, and finally sintered at 380-420°C for 3-5 h to obtain the desired product. To mesoporous nano-silica; wherein the mass ratio of octane, deionized water, hexadecyltrimethylammonium bromide, styrene, 2,2'-azo(2-methylpropylammonium) dihydrochloride, L-lysine and tetraethyl silicate is (31.6-63.2):(100-200):(0.3-0.6):(7.7-15.4):(0.115-0.23):(0.066-0.132):(0.3-0-6).

[0012] Preferably, in step six, the method for recovering nickel is as follows: Nickel in the secondary leaching solution was extracted using 25% P507 to obtain lithium-rich and nickel-rich solutions. The nickel-rich solution was washed with 38-42 g / L sulfuric acid aqueous solution and then evaporated and concentrated to obtain nickel sulfate. The extraction conditions were as follows: P507 organic phase saponification rate 60%-80%, liquid alkali flow rate 0.2-1.0 m³ / h, fore-liquid flow rate 2.0-6.0 m³ / h, and organic phase flow rate 3.0-8.0 m³ / h.

[0013] Preferably, in step seven, the lithium recovery method is as follows: Sodium carbonate was added to a lithium-rich solution to adjust the molar ratio of lithium ions to carbonate ions to 2:1. The mixture was reacted at 80-90℃ for 60-80 min, filtered, washed, and dried to obtain lithium carbonate. In the above process, carbonate ions in sodium carbonate combine with lithium ions through a metathesis reaction to form lithium carbonate precipitate.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves the goal of recovering high-purity manganese sulfate from waste lithium-ion batteries, and also realizes the graded recovery of manganese, nickel, and lithium. Manganese, nickel, and lithium are ultimately separated in the form of manganese dioxide, nickel sulfate, and lithium carbonate, respectively. Manganese dioxide can also be further processed into chemical products such as manganese sulfate. In addition, during the nickel recovery process, high-purity nickel sulfate and lithium carbonate can be prepared by extracting nickel. Therefore, the method of this invention takes into account the graded recovery of multiple valuable metals, conforms to the concept of green environmental protection and sustainable development, and has good economic benefits.

[0015] 2. In the acid leaching process, this invention uses rice husks, a green and natural material, as a raw material to prepare rice husk hydrolysate, which helps to improve the leaching rate of metals during the acid leaching process, thereby achieving efficient metal recovery. Furthermore, the acidity required for leaching of cathode active materials treated with rice husk hydrolysate is significantly reduced, which not only reduces the input of raw materials during the acid leaching process but also reduces the risk of equipment corrosion.

[0016] 3. In the cobalt sulfate recovery process of this invention, a silica-based adsorbent is used, which can efficiently and selectively adsorb cobalt ions to obtain high-purity cobalt sulfate. Furthermore, since methacryloyloxyethyltrimethylammonium chloride is covalently grafted onto mesoporous nano-silica, the problem of low loading rate and easy desorption of methacryloyloxyethyltrimethylammonium chloride on mesoporous nano-silica is solved, thereby improving the adsorption and recovery effect of cobalt ions. In addition, the silica-based adsorbent can be recycled, making it more economical and environmentally friendly.

[0017] 4. In the pretreatment process of waste lithium-ion batteries, this invention achieves the stripping of cathode active materials on the one hand, and on the other hand, aluminum foil, which is often overlooked in traditional recycling processes, is processed into alumina adsorbent by this invention. The alumina adsorbent can efficiently remove fluorides in the leaching solution of cathode active materials during the leaching pretreatment process, thereby improving the purity and recovery rate of subsequent metal products. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the method for recovering high-purity cobalt sulfate from waste lithium-ion batteries according to the present invention; Figure 2 This is a comparison chart of the purity and cobalt recovery rate of cobalt sulfate in Examples 2-4 and Comparative Examples 2-4 of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This embodiment discloses a method for preparing a silica-based adsorbent, including the following steps: Step S1: Disperse 47.4g of octane in 150g of deionized water and stir at 750r / min for 30min at 70℃. Then add 0.45g of hexadecyltrimethylammonium bromide and stir at 70℃ for 5min. Then, add 11.55g of styrene, 0.173g of 2,2'-azo(2-methylpropylamidine) dihydrochloride, 0.099g of L-lysine and 0.45g of tetraethyl silicate in sequence and stir for 4h. After the reaction is completed, centrifuge and wash the obtained solid product four times with methanol. Then, vacuum dry at 75℃ for 3h and finally sinter at 400℃ for 4h to remove surfactant to obtain mesoporous nano silica. 0.15g of mesoporous nano silica was added to 480g of ethanol and sonicated for 20min. Then 1g of 3-mercaptopropyltrimethoxysilane was added and the mixture was stirred for 10h. After the reaction was completed, the mixture was centrifuged and the resulting solid product was washed four times with ethanol and then vacuum dried at 75℃ for 3h to obtain modified mesoporous nano silica. Step S2: Add 0.15g of modified mesoporous nano silica to 480g of ethanol, sonicate for 20min, heat to 70℃, then add 1.9g of methacryloyloxyethyltrimethylammonium chloride and 0.03g of azobisisobutyronitrile, stir and react for 5h. After the reaction is completed, filter, wash and dry to obtain silica-based adsorbent.

[0021] Example 2 This embodiment discloses a method for recovering high-purity cobalt sulfate from spent lithium-ion batteries, comprising the following steps: Step 1: Pre-treatment of used lithium-ion batteries: After cleaning the waste lithium-ion batteries with deionized water, they were soaked in a 10 wt% NaCl aqueous solution for 40 hours for discharge treatment. The entire process was carried out in a fume hood to ensure the safety of subsequent disassembly. After discharge, the batteries were dried in a vacuum oven at 75ºC for 50 hours to ensure that all moisture was removed. Then, the dried batteries were manually disassembled using a small cutting machine to remove impurities such as the casing and separator, and the positive electrode sheet was obtained. The positive electrode sheet was cut into 2cm×2cm fragments and then heated to 500℃ at a heating rate of 5℃ / min for 2.5h in air atmosphere to remove organic matter. It was then passed through a 400-mesh sieve to separate the cathode active material from the aluminum foil based on the density and particle size difference. The finer cathode active material passed through the sieve, while the aluminum foil remained on the sieve, resulting in cathode active material and sieved aluminum foil. The sieved aluminum foil was washed three times with deionized water to obtain clean aluminum foil and washing liquid. The washing liquid was combined, filtered, and dried to obtain aluminum foil fragments. 2g of aluminum foil fragments were dissolved in 150mL of 0.5mol / L sodium hydroxide aqueous solution, and then stirred at 68℃ for 4h. After cooling, the solution was filtered. The pH of the filtrate was adjusted to 5.9 with 38wt% hydrochloric acid aqueous solution at 68℃ with stirring. After stopping stirring, the white precipitate was collected by filtration, washed twice with deionized water, and dried at 55℃ to obtain a white precursor. The white precursor was then heated to 500℃ at a heating rate of 5℃ / min in air atmosphere and calcined for 2.5h to obtain alumina adsorbent. Step 2, Acid Immersion Treatment: After washing and drying, rice husks were ground for 5 minutes to obtain rice husk powder with a particle size of 120 μm. The rice husk powder was added to a 9.2 mol / L sulfuric acid aqueous solution with a solid-liquid mass ratio of 4.5:1. The mixture was stirred at 58 °C and hydrolyzed for 80 minutes. Then, the pH of the system was adjusted to 1 with sodium hydroxide to obtain rice husk hydrolysate. Mix 40g of rice husk hydrolysate with 240g of distilled water, stir, heat to 50℃, then add 12g of cathode active material, then adjust the pH to 1 with 50wt% sulfuric acid aqueous solution, acid leaching treatment for 6h, after the reaction is completed, filter to obtain leachate and leachate residue. Step 3: Leachate Pretreatment Alumina adsorbent was added to the leachate with a solid-liquid ratio of 30 g / L. The pH was adjusted to 2.8 with 0.1 mol / L sodium hydroxide aqueous solution. The adsorption was carried out at 30℃ for 70 min. The leachate was then filtered to obtain the adsorbed leachate. The pH of the adsorption-treated leachate was adjusted to 4.4 using a 0.1 mol / L sodium hydroxide aqueous solution, and a precipitation treatment was performed for 40 min. The leachate was then filtered to remove the filter residue, and the pretreated leachate was obtained. Step 4: Precipitation treatment of manganese: At 24℃, potassium permanganate was added to the pretreated leachate to make the concentration of potassium permanganate 0.007 g / mL. The pH was adjusted to 1.8 with 0.1 mol / L sulfuric acid aqueous solution, and a secondary precipitation treatment was performed for 20 min. After filtration, manganese dioxide precipitate and primary leachate were obtained. Step 5: Recovery of cobalt sulfate: The silica-based adsorbent prepared in Example 1 was added to the primary leachate with a solid-liquid ratio of 30 g / L. Then, sodium nitrite and nitric acid were added to make the concentration of sodium nitrite in the system 0.5 mol / L and the concentration of H+ 0.021 mol / L. Then, a secondary adsorption treatment was carried out at 35°C for 5 h. After filtration, cobalt-containing filter residue and secondary leachate were obtained. The cobalt-containing filter residue washed with deionized water was added to a 1 mol / L HCl aqueous solution with a solid-liquid ratio of 25 g / L. The solution was desorbed at 24 °C for 2.5 h, and then filtered to obtain a cobalt-rich solution and the recovered silica-based adsorbent. At 24°C, 25 wt% ammonia was added to a cobalt-rich solution until no precipitate was formed. The solution was filtered, and the resulting solid product was washed with deionized water and ethanol and then dried to obtain cobalt hydroxide. In a nitrogen atmosphere at 24°C, cobalt hydroxide was mixed with a 1 mol / L sulfuric acid aqueous solution, and the molar ratio of cobalt hydroxide to sulfuric acid was controlled at 1:1. The mixture was stirred for 60 min. After the reaction was completed, the mixture was evaporated, concentrated, cooled and crystallized to obtain high-purity cobalt sulfate. Step Six: Nickel Recovery Nickel was extracted from the secondary leaching solution using 25% P507 extraction to obtain a lithium-rich solution and a nickel-rich solution. The nickel-rich solution was washed with a 38 g / L sulfuric acid aqueous solution and then evaporated and concentrated to obtain nickel sulfate. The extraction conditions were as follows: P507 organic phase saponification rate 60%, liquid alkali flow rate 0.2 m³ / h, foreliquor flow rate 2.0 m³ / h, and organic phase flow rate 3.0 m³ / h. Step 7: Lithium Recovery Sodium carbonate was added to a lithium-rich solution to adjust the molar ratio of lithium ions to carbonate ions to 2:1. The mixture was reacted at 80°C for 80 min, filtered, and the resulting solid product was washed with ultrapure water and dried to obtain lithium carbonate.

[0022] Example 3 This embodiment discloses a method for recovering high-purity cobalt sulfate from spent lithium-ion batteries, comprising the following steps: Step 1: Pre-treatment of used lithium-ion batteries: After cleaning the waste lithium-ion batteries with deionized water, they were soaked in a 10 wt% NaCl aqueous solution for 50 hours for discharge treatment. The entire process was carried out in a fume hood to ensure the safety of subsequent disassembly. After discharge, the batteries were dried in a vacuum oven at 85ºC for 40 hours to ensure that all moisture was removed. Then, the dried batteries were manually disassembled using a small cutting machine to remove impurities such as the casing and separator, and the positive electrode sheet was obtained. The positive electrode sheet was cut into 2cm×2cm fragments and then heated to 520℃ at a heating rate of 5℃ / min in air for 1.5h to remove organic matter. The fragments were then passed through a 500-mesh sieve to separate the cathode active material from the aluminum foil based on the density and particle size difference. The finer cathode active material passed through the sieve, while the aluminum foil remained on the sieve, resulting in cathode active material and sieved aluminum foil. The sieved aluminum foil was then rinsed 5 times with deionized water to obtain clean aluminum foil and washing liquid. The washing liquid was combined, filtered, and dried to obtain aluminum foil fragments. Dissolve 3g of aluminum foil fragments in 250mL of 0.5mol / L sodium hydroxide aqueous solution, stir at 72℃ for 2h, cool, filter the solution, adjust the pH of the filtrate to 6.1 with 38wt% hydrochloric acid aqueous solution at 72℃ with stirring, stop stirring, filter and collect the white precipitate, wash with deionized water 4 times, dry at 65℃ to obtain a white precursor, then heat the white precursor to 700℃ in air at a heating rate of 5℃ / min and calcine for 1.5h to obtain alumina adsorbent; Step 2, Acid Immersion Treatment: After washing and drying, rice husks were ground for 10 minutes to obtain rice husk powder with a particle size of 60 μm. The rice husk powder was added to a 9.2 mol / L sulfuric acid aqueous solution with a solid-liquid mass ratio of 5.5:1. The mixture was stirred at 62℃ and hydrolyzed for 40 minutes. Then, the pH of the system was adjusted to 2 with sodium hydroxide to obtain rice husk hydrolysate. Mix 60g of rice husk hydrolysate with 260g of distilled water, stir, heat to 60℃, then add 15g of cathode active material, then adjust the pH to 2 with 50wt% sulfuric acid aqueous solution, acid leaching treatment for 8h, after the reaction is completed, filter to obtain leachate and leachate residue. Step 3: Leachate Pretreatment Alumina adsorbent was added to the leachate with a solid-liquid ratio of 40 g / L. The pH was adjusted to 3 with 0.1 mol / L sodium hydroxide aqueous solution. The adsorption was carried out at 40℃ for 70 min. The leachate was then filtered to obtain the adsorbed leachate. The pH of the adsorption-treated leachate was adjusted to 4.6 using a 0.1 mol / L sodium hydroxide aqueous solution, and a precipitation treatment was performed for 60 min. The leachate was then filtered to remove the filter residue, resulting in the pretreated leachate. Step 4: Precipitation treatment of manganese: At 26℃, potassium permanganate was added to the pretreated leachate to make the concentration of potassium permanganate 0.009 g / mL. The pH was adjusted to 2 with 0.1 mol / L sulfuric acid aqueous solution, and a secondary precipitation treatment was performed for 30 min. After filtration, manganese dioxide precipitate and primary leachate were obtained. Step 5: Recovery of cobalt sulfate: The silica-based adsorbent prepared in Example 1 was added to the primary leachate with a solid-liquid ratio of 40 g / L. Then, sodium nitrite and nitric acid were added to make the concentration of sodium nitrite in the system 1 mol / L and the concentration of H+ 0.025 mol / L. Then, a secondary adsorption treatment was carried out at 45°C for 4 h. After filtration, cobalt-containing filter residue and secondary leachate were obtained. The cobalt-containing filter residue washed with deionized water was added to a 1.5 mol / L HCl aqueous solution with a solid-liquid ratio of 35 g / L. The solution was desorbed at 28 °C for 1.5 h, filtered, and a cobalt-rich solution and the recovered silica-based adsorbent were obtained. At 28°C, 28 wt% ammonia was added to a cobalt-rich solution until no precipitate was formed. The solution was filtered, and the resulting solid product was washed with deionized water and ethanol and then dried to obtain cobalt hydroxide. In a nitrogen atmosphere at 28°C, cobalt hydroxide was mixed with a 1 mol / L sulfuric acid aqueous solution, and the molar ratio of cobalt hydroxide to sulfuric acid was controlled at 1:1. The mixture was stirred for 30 min. After the reaction was completed, the mixture was evaporated, concentrated, cooled and crystallized to obtain high-purity cobalt sulfate. Step Six: Nickel Recovery Nickel in the secondary leaching solution was extracted using 25% P507 extraction to obtain a lithium-rich solution and a nickel-rich solution. The nickel-rich solution was washed with a 42 g / L sulfuric acid aqueous solution and then evaporated and concentrated to obtain nickel sulfate. The extraction conditions were as follows: P507 organic phase saponification rate 80%, liquid alkali flow rate 1.0 m³ / h, foreliquor flow rate 6.0 m³ / h, and organic phase flow rate 8.0 m³ / h. Step 7: Lithium Recovery Sodium carbonate was added to a lithium-rich solution to adjust the molar ratio of lithium ions to carbonate ions to 2:1. The mixture was reacted at 90°C for 60 min, filtered, and the resulting solid product was washed with ultrapure water and dried to obtain lithium carbonate.

[0023] Example 4 This embodiment discloses a method for recovering high-purity cobalt sulfate from spent lithium-ion batteries, comprising the following steps: Step 1: Pre-treatment of used lithium-ion batteries: After cleaning the waste lithium-ion batteries with deionized water, they were soaked in a 10 wt% NaCl aqueous solution for 45 hours for discharge treatment. The entire process was carried out in a fume hood to ensure the safety of subsequent disassembly. After discharge, the batteries were dried in a vacuum oven at 80ºC for 45 hours to ensure that all moisture was removed. The dried batteries were then manually disassembled using a small cutting machine to remove impurities such as the casing and separator, and the positive electrode sheet was obtained. The positive electrode sheet was cut into 2cm×2cm fragments and then heated to 510℃ in air at a heating rate of 5℃ / min for 2 hours to remove organic matter. The fragments were then passed through a 450-mesh sieve. Based on the density and particle size difference between the cathode active material and the aluminum foil, the cathode active material was separated from the aluminum foil. The finer cathode active material passed through the sieve, while the aluminum foil remained on the sieve, resulting in cathode active material and sieved aluminum foil. The sieved aluminum foil was rinsed four times with deionized water to obtain clean aluminum foil and washing liquid. The washing liquid was combined, filtered, and dried to obtain aluminum foil fragments. 2.5g of aluminum foil fragments were dissolved in 200mL of 0.5mol / L sodium hydroxide aqueous solution, and then stirred at 70℃ for 3h. After cooling, the solution was filtered. The pH of the filtrate was adjusted to 6 with 38wt% hydrochloric acid aqueous solution at 70℃ with stirring. After stopping stirring, the white precipitate was collected by filtration, washed 3 times with deionized water, and dried at 60℃ to obtain a white precursor. The white precursor was then heated to 600℃ at a heating rate of 5℃ / min in air atmosphere and calcined for 2h to obtain alumina adsorbent. Step 2, Acid Immersion Treatment: After washing and drying, the rice husks were ground for 8 minutes to obtain rice husk powder with a particle size of 90 μm. The rice husk powder was added to a 9.2 mol / L sulfuric acid aqueous solution with a solid-liquid mass ratio of 5:1. The mixture was stirred at 60°C and hydrolyzed for 60 minutes. Then, the pH of the system was adjusted to 1.5 with sodium hydroxide to obtain rice husk hydrolysate. Mix 50g of rice husk hydrolysate with 250g of distilled water, stir, heat to 55℃, then add 13.5g of cathode active material, then adjust the pH to 1.5 with 50wt% sulfuric acid aqueous solution, and acid leaching for 7h. After the reaction is complete, filter to obtain leachate and leachate residue. Step 3: Leachate Pretreatment Alumina adsorbent was added to the leachate with a solid-liquid ratio of 35 g / L. The pH was adjusted to 2.9 with 0.1 mol / L sodium hydroxide aqueous solution. The adsorption was carried out at 35℃ for 80 min. The leachate was then filtered to obtain the adsorbed leachate. The pH of the adsorption-treated leachate was adjusted to 4.5 using a 0.1 mol / L sodium hydroxide aqueous solution, and a precipitation treatment was performed for 50 min. The leachate was then filtered to remove the filter residue, resulting in the pretreated leachate. Step 4: Precipitation treatment of manganese: At 25℃, potassium permanganate was added to the pretreated leachate to make the concentration of potassium permanganate 0.008 g / mL. The pH was adjusted to 1.9 with 0.1 mol / L sulfuric acid aqueous solution, and a secondary precipitation treatment was performed for 25 min. After filtration, manganese dioxide precipitate and primary leachate were obtained. Step 5: Recovery of cobalt sulfate: The silica-based adsorbent prepared in Example 1 was added to the primary leachate with a solid-liquid ratio of 35 g / L. Then, sodium nitrite and nitric acid were added to make the concentration of sodium nitrite in the system 0.8 mol / L and the concentration of H+ 0.023 mol / L. Then, a secondary adsorption treatment was carried out at 40°C for 4.5 h. After filtration, cobalt-containing filter residue and secondary leachate were obtained. The cobalt-containing filter residue washed with deionized water was added to a 1.3 mol / L HCl aqueous solution with a solid-liquid ratio of 30 g / L. The solution was desorbed at 26 °C for 2 h and then filtered to obtain a cobalt-rich solution and the recovered silica-based adsorbent. At 26°C, 26.5 wt% ammonia was added to a cobalt-rich solution until no precipitate was formed. The solution was filtered, and the resulting solid product was washed with deionized water and ethanol and then dried to obtain cobalt hydroxide. In a nitrogen atmosphere at 26°C, cobalt hydroxide was mixed with a 1 mol / L sulfuric acid aqueous solution, and the molar ratio of cobalt hydroxide to sulfuric acid was controlled at 1:1. The mixture was stirred for 45 min. After the reaction was completed, the mixture was evaporated, concentrated, cooled and crystallized to obtain high-purity cobalt sulfate. Step Six: Nickel Recovery Nickel in the secondary leaching solution was extracted using 25% P507 extraction to obtain a lithium-rich solution and a nickel-rich solution. The nickel-rich solution was washed with a 40 g / L sulfuric acid aqueous solution and then evaporated and concentrated to obtain nickel sulfate. The extraction conditions were as follows: P507 organic phase saponification rate 70%, liquid alkali flow rate 0.6 m³ / h, foreliquor flow rate 4.0 m³ / h, and organic phase flow rate 5.5 m³ / h. Step 7: Lithium Recovery Sodium carbonate was added to a lithium-rich solution to adjust the molar ratio of lithium ions to carbonate ions to 2:1. The mixture was reacted at 85°C for 70 min, filtered, and the resulting solid product was washed with ultrapure water and dried to obtain lithium carbonate.

[0024] Comparative Example 1 This embodiment discloses a method for preparing a silica-based adsorbent, including the following steps: Step S1: Disperse 47.4g of octane in 150g of deionized water and stir at 750r / min for 30min at 70℃. Then add 0.45g of hexadecyltrimethylammonium bromide and stir at 70℃ for 4-6min. Then, add 11.55g of styrene, 0.173g of 2,2'-azo(2-methylpropylamidine) dihydrochloride, 0.099g of L-lysine and 0.45g of tetraethyl silicate in sequence and stir for 4h. After the reaction is completed, centrifuge and wash the obtained solid product with methanol 4 times. Then, vacuum dry at 75℃ for 3h and finally sinter at 400℃ for 4h to remove surfactant to obtain mesoporous nano silica. Step S2: Add 0.15g of mesoporous nano silica to 480g of ethanol, sonicate for 20min, add 1.9g of methacryloyloxyethyltrimethylammonium chloride, stir at 25℃ for 1h to ensure full contact between the mesoporous nano silica and methacryloyloxyethyltrimethylammonium chloride, heat to 40℃, then evacuate to 0.5bar, and then evaporate the solvent to obtain the silica-based adsorbent.

[0025] Comparative Example 2 Compared with Example 4, Comparative Example 2 did not perform an adsorption treatment on the leachate with alumina adsorbent during the leachate pretreatment process, while other conditions remained unchanged.

[0026] Comparative Example 3 Compared with Example 4, Comparative Example 3 did not add rice husk hydrolysate during the acid soaking process, while other conditions remained unchanged.

[0027] Comparative Example 4 Compared with Example 4, Comparative Example 4 used the silica-based adsorbent prepared in Comparative Example 1 instead of the silica-based adsorbent in Example 1 during the recovery of cobalt sulfate, while keeping all other conditions unchanged.

[0028] In the above embodiments and comparative examples, the spent lithium-ion batteries are NCM523 batteries with the chemical formula LiNi. 0.5 Co 0.2 Mn 0.3 O2.

[0029] Experimental Example I. Leaching Rate Test: Following the methods of Examples 2-4 and Comparative Examples 2-4, after acid leaching treatment, the leaching rate of each metal was calculated according to the following formula (1): Equation (1); In equation (1), r e Let m be the leaching rate of each metal. s m0 represents the mass of each metal in the leachate, and m0 represents the mass of each metal in the cathode active material. II. Purity test of cobalt sulfate: The purity of the cobalt sulfate samples obtained in Examples 2-4 and Comparative Examples 2-4 was tested using a microwave inductively coupled plasma atomic emission spectrometer. III. Cobalt sulfate recovery rate: Following the methods of Examples 2-4 and Comparative Examples 2-4, the cobalt recovery rate in each example and comparative example was calculated according to the following formula (2): Co ): Equation (2); In formula (2), m2 is the mass of cobalt in the cobalt sulfate product, and m0 is the mass of metallic cobalt in the cathode active material; The calculation results are shown in Table 1: Table 1

[0030] As can be seen from the test results in Table 1, the method of Examples 2-4 of the present invention can recover high-purity cobalt sulfate from waste lithium-ion batteries. Furthermore, the leaching rates of Li, Ni, Co and Mn in the method of the present invention all exceed 98%, achieving synergistic leaching of the four metals and thus improving the metal recovery rate.

[0031] As can be seen from the comparison between Comparative Example 2 and Example 4, adding alumina adsorbent to the leachate removes fluorine-containing compounds from the leachate. Then, by adjusting the pH of the system to 4.4-4.6, iron and aluminum impurities are removed. Therefore, by pretreating the leachate, fluorine-containing compounds, iron, and aluminum impurities can be removed from the leachate, which helps to improve the purity and recovery rate of the product. As can be seen from the comparison between Comparative Example 3 and Example 4, in the low-acid system of acid leaching treatment, the addition of rice husk hydrolysate will convert the high-valence key metals into easily leached low-valence metals, thereby improving the leaching rate and recovery rate of the metals. As can be seen from the comparison between Comparative Example 4 and Example 4, in the cobalt sulfate recovery process, the use of silica-based adsorbent can achieve efficient and selective adsorption of cobalt ions, thereby obtaining high-purity cobalt sulfate. Grafting methacryloyloxyethyltrimethylammonium chloride onto mesoporous nano-silica in the form of covalent bonds solves the problems of low loading rate and easy desorption of methacryloyloxyethyltrimethylammonium chloride on mesoporous nano-silica, thereby improving the adsorption effect of cobalt ions. This will affect the recovery rate of cobalt, but has little impact on the purity of cobalt sulfate.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for recovering high-purity cobalt sulfate from spent lithium-ion batteries, characterized in that, Includes the following steps: Step 1: Pretreatment of waste lithium-ion batteries: The waste lithium-ion batteries are pretreated to obtain cathode active materials and alumina adsorbent. Step 2, Acid Leaching Treatment: The rice husk powder is hydrolyzed with sulfuric acid to obtain rice husk hydrolysate; the rice husk hydrolysate, cathode active material, and sulfuric acid are mixed and acid leached to obtain leachate and leachate residue; Step 3: Leachate pretreatment: After the leachate undergoes an adsorption treatment with alumina adsorbent, the pH is adjusted and a precipitation treatment is performed to obtain the pretreated leachate. Step 4: Precipitation treatment of manganese: Add potassium permanganate to the pretreated leachate for secondary precipitation treatment to obtain manganese dioxide precipitate and primary leachate; Step 5, Cobalt sulfate recovery: Add silica-based adsorbent to the primary leachate for secondary adsorption treatment to obtain cobalt-containing filter residue and secondary leachate; use the cobalt-containing filter residue as raw material to prepare high-purity cobalt sulfate; The preparation method of the silica adsorbent includes the following steps: Step S1: Prepare mesoporous nano-silica; Modify the mesoporous nano-silica with 3-mercaptopropyltrimethoxysilane to obtain modified mesoporous nano-silica. Step S2: Modified mesoporous nano-silica reacts with methacryloyloxyethyltrimethylammonium chloride to obtain a silica-based adsorbent; Step 6, Nickel Recovery: Nickel ions in the secondary leaching solution are extracted using P507 to obtain a lithium-rich solution and a nickel-rich solution. The nickel-rich solution is then post-treated to obtain nickel sulfate. Step 7, Lithium Recovery: Add sodium carbonate to the lithium-rich solution and react to obtain lithium carbonate.

2. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, The method for pretreating waste lithium-ion batteries in step one includes the following steps: Positive electrode sheets are obtained by dismantling waste lithium-ion batteries; the positive electrode sheets are heated to 500-520℃ in air atmosphere and heat-treated for 1.5-2.5 hours, and then passed through a 400-500 mesh sieve to obtain cathode active material and sieved aluminum foil; the sieved aluminum foil is washed with deionized water 3-5 times to obtain clean aluminum foil and washing liquid, the washing liquid is combined, filtered, and dried to obtain aluminum foil fragments; Aluminum foil fragments and 0.5 mol / L sodium hydroxide aqueous solution were mixed at a mass ratio of (2-3):(150-250), stirred at 68-72℃ for 2-4 h, cooled, and filtered. The pH of the filtrate was adjusted to 5.9-6.1 at 68-72℃, filtered, and the resulting white precipitate was collected, washed, and dried to obtain a white precursor. The white precursor was then calcined at 500-700℃ for 1.5-2.5 h in air to obtain alumina adsorbent.

3. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step two, the acid leaching treatment method is as follows: Add rice husk powder to a 9.2 mol / L sulfuric acid aqueous solution at a solid-liquid mass ratio of (4.5-5.5):1, stir at 58-62℃, hydrolyze for 40-80 min, and then adjust the pH to 1-2 to obtain rice husk hydrolysate. Mix rice husk hydrolysate with distilled water, stir, heat to 50-60℃, then add cathode active material, and adjust the pH to 1-2 with 50wt% sulfuric acid aqueous solution. Acid leaching treatment for 6-8 hours. After the reaction is completed, filter to obtain leachate and leachate residue; wherein, the mass ratio of rice husk hydrolysate, distilled water and cathode active material is (40-60):(240-260):(12-15).

4. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step three, the method for pretreating the leachate is as follows: Add the alumina adsorbent to the leachate with a solid-liquid ratio of 30-40 g / L, adjust the pH to 2.8-3 with 0.1 mol / L sodium hydroxide aqueous solution, perform an adsorption treatment at 30-40℃ for 70-90 min, filter, and obtain the adsorbed leachate. The pH of the adsorption-treated leachate was adjusted to 4.4-4.6, and a precipitation treatment was performed for 40-60 minutes. After filtration, the pretreated leachate was obtained.

5. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step four, the method for precipitating manganese is as follows: At 24-26℃, potassium permanganate is added to the pretreated leachate to make the concentration of potassium permanganate 0.007-0.009 g / mL, the pH is adjusted to 1.8-2, a second precipitation treatment is performed for 20-30 min, and then filtered to obtain manganese dioxide precipitate and primary leachate.

6. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step five, the method for recovering cobalt sulfate is as follows: A silica-based adsorbent was added to the primary leachate at a solid-liquid ratio of 30-40 g / L. Then, sodium nitrite and nitric acid were added to achieve a sodium nitrite concentration of 0.5-1 mol / L in the system. + The concentration was 0.021-0.025 mol / L, and then a secondary adsorption treatment was carried out at 35-45℃ for 4-5 hours. After filtration, cobalt-containing filter residue and secondary leachate were obtained. Add the cobalt-containing filter residue to a 1-1.5 mol / L HCl aqueous solution with a solid-liquid ratio of 25-35 g / L, desorb at 24-28℃ for 1.5-2.5 h, filter, and obtain a cobalt-rich solution and recovered silica-based adsorbent. At 24-28℃, 25-28wt% ammonia was added to the cobalt-rich solution until no precipitate was formed. The solution was filtered, and the resulting solid product was washed with deionized water and ethanol and then dried to obtain cobalt hydroxide. In a nitrogen atmosphere at 24-28℃, cobalt hydroxide is mixed with a 1 mol / L sulfuric acid aqueous solution, and the molar ratio of cobalt hydroxide to sulfuric acid is controlled at 1:

1. The mixture is stirred for 30-60 min. After the reaction is completed, the mixture is evaporated, concentrated, cooled and crystallized to obtain high-purity cobalt sulfate.

7. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step five, the preparation method of the silica-based adsorbent is as follows: Step S1: Add mesoporous nano-silica to ethanol, sonicate, then add 3-mercaptopropyltrimethoxysilane, stir and react for 8-12 hours, purify the product, and obtain modified mesoporous nano-silica; wherein, the mass ratio of the mesoporous nano-silica, ethanol and 3-mercaptopropyltrimethoxysilane is (0.1-0.2):(320-640):(0.8-1.2); Step S2: Add modified mesoporous nano silica to ethanol, sonicate, heat to 65-75℃, then add methacryloyloxyethyltrimethylammonium chloride and azobisisobutyronitrile, stir and react for 4-6 hours, purify the product, and obtain silica-based adsorbent; wherein, the mass ratio of the modified mesoporous nano silica, ethanol, methacryloyloxyethyltrimethylammonium chloride and azobisisobutyronitrile is (0.1-0.2):(320-640):(1.2-2.6):(0.02-0.04).

8. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 7, characterized in that, The method for preparing the mesoporous nano-silica: Octane was dispersed in deionized water and stirred at 65-75°C for 20-40 min. Then, hexadecyltrimethylammonium bromide was added and stirred at 65-75°C for 4-6 min. Next, styrene, 2,2'-azo(2-methylpropylamidine) dihydrochloride, L-lysine, and tetraethyl silicate were added sequentially, and the mixture was stirred for 3.5-4.5 h. After the reaction was complete, the mixture was centrifuged, washed, dried, and finally sintered at 380-420°C for 3-5 h to obtain the desired product. To mesoporous nano-silica; wherein the mass ratio of octane, deionized water, hexadecyltrimethylammonium bromide, styrene, 2,2'-azo(2-methylpropylammonium) dihydrochloride, L-lysine and tetraethyl silicate is (31.6-63.2):(100-200):(0.3-0.6):(7.7-15.4):(0.115-0.23):(0.066-0.132):(0.3-0-6).

9. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step six, the method for recovering nickel is as follows: Nickel in the secondary leaching solution was extracted using 25% P507 to obtain lithium-rich and nickel-rich solutions. The nickel-rich solution was washed with 38-42 g / L sulfuric acid aqueous solution and then evaporated and concentrated to obtain nickel sulfate. The extraction conditions were as follows: P507 organic phase saponification rate 60%-80%, liquid alkali flow rate 0.2-1.0 m³ / h, fore-liquid flow rate 2.0-6.0 m³ / h, and organic phase flow rate 3.0-8.0 m³ / h.

10. The method for recovering high-purity cobalt sulfate from spent lithium-ion batteries according to claim 1, characterized in that, In step seven, the lithium recovery method is as follows: Sodium carbonate was added to a lithium-rich solution to adjust the molar ratio of lithium ions to carbonate ions to 2:

1. The mixture was reacted at 80-90℃ for 60-80 min, filtered, washed, and dried to obtain lithium carbonate.

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