Method for recycling valuable materials from waste ternary lithium batteries

Abstract

The invention discloses a method for recovering a valuable material from a waste ternary lithium battery, which directly uses a lithium battery inner core as a roasting raw material, simplifies a pretreatment process flow, improves the overall recovery process efficiency, and performs low-temperature reduction roasting by using pyrolysis tail gas generated by pyrolysis of a battery material (the lithium battery inner core) to realize waste reutilization. The organic binder in the organic diaphragm and the positive electrode material can be effectively removed, meanwhile, metal elements in the positive electrode material can be reduced, high-valence metal oxide can be reduced into metal elementary substances, in the subsequent leaching process, use of a reducing agent can be avoided, the metal ion leaching rate in the subsequent water leaching and acid leaching process is increased, and the leaching efficiency is improved. Efficient separation and recovery of lithium, nickel, cobalt, manganese, copper foil, aluminum foil and graphite are realized, and maximization of economic benefits and environmental benefits is realized.

Description

Technical Field:

[0001] The present invention relates to the field of recycling of waste ternary lithium-ion batteries, and specifically relates to a method for recycling valuable materials from waste ternary lithium batteries. Background Art:

[0002] Lithium-ion batteries are widely used in industries and fields such as electronic tools, electric vehicles, aerospace, etc. due to their advantages such as high energy density, long cycle life, and low self-discharge rate. In recent years, the demand and production of lithium-ion batteries have still been increasing. Lithium-ion batteries usually enter the retired state after 5 to 8 years of normal use. If these retired or scrapped lithium-ion batteries are not properly processed, heavy metals, organic materials, toxic and harmful substances, etc. in them will cause pollution to soil, water sources, etc., and will also cause waste of resources and thus bring economic losses.

[0003] Before recycling waste lithium batteries, it is necessary to preprocess the waste lithium-ion batteries to obtain raw materials for recycling. Previous patents have all focused on the recycling of cathode powder materials. For example, Chinese invention patent (publication number: CN119410895A) discloses that using waste lithium-ion battery black powder as raw material and aminosulfonic acid as roasting agent, through processes such as roasting for carbon removal, metal extraction, water leaching, etc., a leaching solution and leaching residue containing two or more elements among lithium, nickel, cobalt, manganese, iron, and aluminum are obtained. However, obtaining cathode powder materials from lithium-ion batteries containing components such as cathode sheets, separators, electrolytes, anode sheets, and casings and having a certain remaining charge requires many steps such as discharging, disassembling, pulverizing, separating, etc., which will reduce the recycling efficiency and increase the recycling cost.

[0004] Currently, the research on the recovery of valuable metals in waste cathode materials of lithium batteries mainly focuses on hydrometallurgical recovery, followed by pyrometallurgical recovery. The hydrometallurgical recovery process uses leaching agents such as acid or alkali solutions and reducing agents to act together to leach the metals in the cathode material. This process has high metal recovery rate and low energy consumption. However, the large amount of leaching agents and reducing agents used is prone to corrode equipment and produce a large amount of wastewater. If not properly treated, it is easy to cause secondary pollution. The pyrometallurgical recovery process directly smelts the cathode material at high temperature. Due to the short reaction time, large processing capacity, and simple process, it is widely used in the industrial recovery of waste lithium-ion batteries. However, the pyrometallurgical recovery process is a high-energy-consuming process that produces a large amount of waste gas. And because lithium elements are often mixed with smelting slag, they cannot be effectively recovered. Combining pyrometallurgy and hydrometallurgy can achieve process complementarity, improve metal recovery rate, reduce energy consumption, and improve the adaptability to battery raw material types. CN116683082A discloses a method for recovering valuable materials from waste lithium batteries by microwave-assisted pyrometallurgy-hydrometallurgy combined process. Using the pyrometallurgy-hydrometallurgy combined process and supplemented by microwave heating means, the advantages of the pyrometallurgical process and the hydrometallurgical process are fully exerted. This method has low energy consumption and high efficiency compared with the traditional pyrometallurgical recovery process, and has a short cycle and cost savings compared with the traditional hydrometallurgical recovery process. However, this method still requires sorting electrode sheets, casings, and diaphragms, and the positive electrode sheets also need to be initially crushed, and then finely crushed and screened to obtain positive electrode black powder. The steps are cumbersome. In addition, step (6) microwave reduction roasting also requires the introduction of expensive hydrogen gas. The waste gas generated during the microwave pyrolysis of the positive electrode black powder in an inert gas atmosphere in step (5) and the microwave reduction roasting process in step (6) is collected and treated to meet the atmospheric emission standards before being discharged. This pyrolysis waste gas is not effectively utilized, resulting in waste of resources. Summary of the Invention:

[0005] The purpose of the present invention is to provide a method for recovering valuable materials from waste ternary lithium batteries, realizing resource reuse, simplifying the recovery process flow, reducing energy consumption, and improving resource recovery rate, and solving the problems of cumbersome steps, high cost, and low resource recovery efficiency in the prior art.

[0006] The present invention is realized through the following technical solutions:

[0007] A method for recovering valuable materials from waste ternary lithium batteries, comprising the following steps:

[0008] 1) Pretreatment: Immerse the waste ternary lithium battery in 5% NaCl solution to fully discharge, and then disassemble the casing to obtain the lithium battery core, which includes components such as a positive electrode, a diaphragm, an electrolyte, and a negative electrode;

[0009] 2) Reduction roasting: Place the inner core of the lithium battery in a sealed tubular furnace at a temperature of 350 - 750 °C, preferably 450 - 650 °C, and conduct sufficient low-temperature reduction roasting under the pyrolysis tail gas atmosphere. The roasting time is 1 - 6 h, preferably 5 - 6 h, the heating rate is 5 - 30 °C / min, preferably 5 - 20 °C / min, and collect the tail gas for reuse in the next reduction roasting cycle. The obtained roasted product is crushed and sieved through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris;

[0010] 3) Water leaching: Use mechanical stirring to fully mix and leach the roasted powder obtained in step 2) with water at room temperature. After filtration, filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain water leaching residue;

[0011] 4) Acid leaching: Use mechanical stirring to fully mix and leach the water leaching residue obtained in step 3) with an acid solution. After filtration, filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid leaching residue, and both the filtrate and the acid leaching residue are used for further recovery and purification of resources.

[0012] Preferably, in step 3), the mechanical stirring rate is 200 - 500 r / min, preferably 300 - 500 r / min, the solid-liquid ratio during water leaching is 10 - 50 g / L, preferably 10 - 30 g / L, and the water leaching time is 6 - 12 h, preferably 10 - 12 h.

[0013] The water leaching filtrate in step 3) is obtained by vacuum distillation to obtain Li 2 CO 3 .

[0014] Preferably, the acid in step 4) is one of sulfuric acid, citric acid, and p-toluenesulfonic acid.

[0015] Preferably, the acid concentration in step 4) is 0.1 - 1.0 mol / L.

[0016] Preferably, in step 4), the mechanical stirring rate is 200 - 500 r / min, the solid-liquid ratio during acid leaching is 10 - 50 g / L, the acid leaching temperature is 50 - 90 °C, preferably 70 - 90 °C, and the acid leaching time is 60 - 120 min.

[0017] The main component of the acid leaching residue is graphite, and the acid leaching filtrate is rich in nickel, cobalt, and manganese ions.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. Directly use the inner core of the lithium battery as the roasting raw material, without the need to separate the electrode sheet, copper foil / aluminum foil, and separator, nor the need to perform primary crushing and then fine crushing and screening on the positive electrode sheet to obtain positive electrode black powder, which can simplify the pretreatment process flow and improve the overall recovery process efficiency.

[0020] 2. The present invention directly uses lithium battery core as the raw material for roasting. The waste lithium battery core contains a large amount of organic materials, such as electrolytes, separators and binders, etc. These substances will pyrolyze at a high temperature of 350-750℃ to produce CO 2 , CO and H 2 The pyrolysis tail gas, including the reducing gases CO and H 2 The negative electrode material graphite can reduce the high-valent metal compounds in the positive electrode material into metal elements or low-valent metal compounds through gas phase reduction and carbon thermal reduction reactions. In the subsequent leaching process, the use of reducing agents can be avoided, and the metal ion leaching rate in the subsequent water leaching and acid leaching processes can be improved, thereby achieving efficient separation and recovery of lithium, nickel, cobalt, manganese, copper foil, aluminum foil and graphite, and maximizing economic and environmental benefits. Description of the drawings:

[0021] Figure 1 It is a flow chart of the present invention. Specific implementation method:

[0022] The following is a further description of the present invention, rather than a limitation of the present invention.

[0023] Embodiment 1:

[0024] Process such as Figure 1 As shown, firstly, the waste ternary lithium battery is fully discharged in a 5% NaCl solution, and then the outer shell is removed to obtain the lithium battery core; the lithium battery core is placed in a sealed tube furnace, heated to 650°C at a rate of 5°C / min, and roasted in a pyrolysis tail gas atmosphere for 5 hours to obtain a roasted product, and the roasted product is crushed and passed through a 200-mesh sieve to obtain a roasted powder and copper-aluminum foil scraps; the roasted powder and water are mixed at a solid-liquid ratio of 10g / L and a stirring rate of 500r / min, stirring at room temperature for 12h, the lithium leaching rate is 72.08%; stirring the water leaching residue and citric acid at 90℃ for 120min at 500r / min, the citric acid concentration is 0.5mol / L, the solid-liquid ratio is 10g / L, and the acid leaching filtrate and filter residue are obtained after filtration. The filter residue is washed and dried to obtain the acid leaching residue. The main component of the acid leaching residue is graphite. The acid leaching filtrate is rich in nickel, cobalt and manganese ions. The acid leaching filtrate and acid leaching residue are further recovered and purified. The leaching rates of nickel, cobalt and manganese are 89.52%, 90.82% and 93.41% respectively.

[0025] Embodiment 2:

[0026] First, fully discharge the waste ternary lithium battery in a 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery. Place the inner core of the lithium battery in a sealed tube furnace and heat it to 750°C at a rate of 30°C / min, and conduct roasting in the pyrolysis tail gas atmosphere for 6 hours to obtain a roasted product. Crush the roasted product and sieve it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris. Stir the roasted powder and water at a solid-liquid ratio of 50 g / L and a stirring rate of 200 r / min at room temperature for 10 hours, and the lithium leaching rate is 23.25%. Stir the water-leached residue and sulfuric acid at 200 r / min at 50°C for 60 minutes, with a sulfuric acid concentration of 0.8 mol / L and a solid-liquid ratio of 50 g / L. After filtration, acid-leached filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid-leached residue. The main component of the acid-leached residue is graphite, and the acid-leached filtrate is rich in nickel, cobalt, and manganese ions. The leaching rates of nickel, cobalt, and manganese are 55.35%, 53.82%, and 73.40% respectively.

[0027] Example 3:

[0028] First, fully discharge the waste ternary lithium battery in a 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery. Place the inner core of the lithium battery in a sealed tube furnace and heat it to 450°C at a rate of 10°C / min, and conduct roasting in the pyrolysis tail gas atmosphere for 6 hours to obtain a roasted product. Crush the roasted product and sieve it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris. Stir the roasted powder and water at a solid-liquid ratio of 10 g / L and a stirring rate of 500 r / min at room temperature for 12 hours, and the lithium leaching rate is 86.23%. Stir the water-leached residue and sulfuric acid at 300 r / min at 90°C for 120 minutes, with a sulfuric acid concentration of 1.0 mol / L and a solid-liquid ratio of 20 g / L. After filtration, acid-leached filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid-leached residue. The main component of the acid-leached residue is graphite, and the acid-leached filtrate is rich in nickel, cobalt, and manganese ions. The leaching rates of nickel, cobalt, and manganese are 99.81%, 99.52%, and 99.68% respectively.

[0029] Example 4:

[0030] First, fully discharge the waste ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery; place the inner core of the lithium battery in a sealed tube furnace, heat it to 350 °C at a rate of 10 °C / min, and conduct roasting under the pyrolysis tail gas atmosphere for 6 hours to obtain a roasted product. Crush the roasted product and sieve it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris; stir the roasted powder and water at a solid-liquid ratio of 20 g / L and a stirring rate of 300 r / min at room temperature for 12 hours, and the lithium leaching rate is 70.65%; stir the water-leached residue and citric acid at 300 r / min at 90 °C for 80 minutes, with the citric acid concentration of 0.5 mol / L and the solid-liquid ratio of 20 g / L. After filtration, acid-leached filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid-leached residue. The main component of the acid-leached residue is graphite, and the acid-leached filtrate is rich in nickel, cobalt, and manganese ions. The leaching rates of nickel, cobalt, and manganese are 87.25%, 88.60%, and 96.83% respectively.

[0031] Example 5:

[0032] First, fully discharge the waste ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery; place the inner core of the lithium battery in a sealed tube furnace, heat it to 450 °C at a rate of 15 °C / min, and conduct roasting under the pyrolysis tail gas atmosphere for 3 hours to obtain a roasted product. Crush the roasted product and sieve it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris; stir the roasted powder and water at a solid-liquid ratio of 20 g / L and a stirring rate of 500 r / min at room temperature for 8 hours, and the lithium leaching rate is 57.46%; stir the water-leached residue and p-toluenesulfonic acid at 300 r / min at 70 °C for 100 minutes, with the p-toluenesulfonic acid concentration of 0.2 mol / L and the solid-liquid ratio of 30 g / L. After filtration, acid-leached filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid-leached residue. The main component of the acid-leached residue is graphite, and the acid-leached filtrate is rich in nickel, cobalt, and manganese ions. The leaching rates of nickel, cobalt, and manganese are 84.25%, 83.60%, and 90.83% respectively.

[0033] Example 6:

[0034] First, fully discharge the waste ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery; place the inner core of the lithium battery in a sealed tube furnace, heat it to 350 °C at a rate of 10 °C / min, and carry out roasting in the pyrolysis tail gas atmosphere for 2 h to obtain a roasted product. Then, crush the roasted product and pass it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris; stir the roasted powder and water at a solid-liquid ratio of 50 g / L and a stirring rate of 400 r / min at room temperature for 6 h, and the lithium leaching rate is 50.30%; stir the water-leached residue and p-toluenesulfonic acid at 300 r / min at 50 °C for 60 min, the concentration of p-toluenesulfonic acid is 0.1 mol / L, and the solid-liquid ratio is 50 g / L. After filtration, acid-leached filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid-leached residue. The main component of the acid-leached residue is graphite, and the acid-leached filtrate is rich in nickel, cobalt, and manganese ions. The leaching rates of nickel, cobalt, and manganese are 41.21%, 39.85%, and 69.42% respectively.

[0035] Example 7:

[0036] First, fully discharge the waste ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery; place the inner core of the lithium battery in a sealed tube furnace, heat it to 550 °C at a rate of 20 °C / min, and carry out roasting in the pyrolysis tail gas atmosphere for 6 h to obtain a roasted product. Then, crush the roasted product and pass it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris; stir the roasted powder and water at a solid-liquid ratio of 30 g / L and a stirring rate of 200 r / min at room temperature for 10 h, and the lithium leaching rate is 88.31%; stir the water-leached residue and sulfuric acid at 300 r / min at 70 °C for 100 min, the concentration of sulfuric acid is 0.2 mol / L, and the solid-liquid ratio is 10 g / L. After filtration, acid-leached filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid-leached residue. The main component of the acid-leached residue is graphite, and the acid-leached filtrate is rich in nickel, cobalt, and manganese ions. The leaching rates of nickel, cobalt, and manganese are 88.84%, 87.43%, and 95.63% respectively.

[0037] Example 8:

[0038] First, fully discharge the waste ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery. Place the inner core of the lithium battery in a sealed tube furnace, heat it to 550 °C at a rate of 10 °C / min, and conduct roasting under the pyrolysis tail gas atmosphere for 6 h to obtain a roasted product. Crush the roasted product and pass it through a 200-mesh sieve to obtain roasted powder and copper-aluminum foil debris. Stir the roasted powder and water at a solid-liquid ratio of 20 g / L and a stirring rate of 300 r / min at room temperature for 12 h, and the lithium leaching rate is 89.00%. Stir the water leaching residue and citric acid at 90 °C for 80 min at a stirring rate of 300 r / min, with a citric acid concentration of 0.5 mol / L and a solid-liquid ratio of 20 g / L. After filtration, acid leaching filtrate and filter residue can be obtained. The filter residue is washed and dried to obtain acid leaching residue, and the main component of the acid leaching residue is graphite. The acid leaching filtrate is rich in nickel, cobalt, and manganese ions, and the leaching rates of nickel, cobalt, and manganese are 98.82%, 99.03%, and 97.06% respectively.

[0039] Comparative Example 1:

[0040] First, fully discharge the waste ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery. After naturally air-drying the inner core of the lithium battery, crush it and pass it through a 200-mesh sieve to obtain a mixed powder and copper-aluminum foil debris. Stir the mixed powder and water at a solid-liquid ratio of 20 g / L and a stirring rate of 300 r / min at room temperature for 12 h, and the lithium leaching rate is 13.84%. Stir the water leaching residue and citric acid at 90 °C for 80 min at a stirring rate of 300 r / min, with a citric acid concentration of 0.5 mol / L and a solid-liquid ratio of 20 g / L. After filtration, acid leaching filtrate and filter residue can be obtained. The acid leaching filtrate is rich in nickel, cobalt, and manganese ions, and the leaching rates of nickel, cobalt, and manganese are 27.90%, 27.58%, and 25.98% respectively.

[0041] Comparing Comparative Example 1 and Example 4, it can be seen that the inner core of the lithium battery can significantly improve the leaching rate of metals through reduction roasting compared with natural air-drying.

[0042] Comparative Example 2:

[0043] First, fully discharge the used ternary lithium battery in 5% NaCl solution, then disassemble the outer shell to obtain the inner core of the lithium battery. Place the inner core of the lithium battery in a sealed tubular furnace and calcine it under a nitrogen atmosphere. Heat it up to 550 °C at a rate of 10 °C / min and calcine for 6 h to obtain a calcined product. Crush the calcined product and sieve it through a 200-mesh sieve to obtain calcined powder and copper-aluminum foil debris. Stir the calcined powder and water at a solid-liquid ratio of 20 g / L and a stirring rate of 300 r / min at room temperature for 10 h, and the lithium leaching rate is 55.65%. Stir the water leaching residue and citric acid at 300 r / min at 90 °C for 80 min, with a citric acid concentration of 0.5 mol / L and a solid-liquid ratio of 20 g / L. After filtration, acid leaching filtrate and filter residue can be obtained. The acid leaching filtrate is rich in nickel, cobalt, and manganese ions, and the nickel, cobalt, and manganese leaching rates are 43.16%, 50.16%, and 98.76% respectively.

[0044] Comparing Comparative Example 2 and Example 8, it can be seen that compared with the inert nitrogen atmosphere, using the pyrolysis tail gas generated by the thermal decomposition of the inner core of the lithium battery for low-temperature reduction roasting can reduce the metal elements in the positive electrode material while removing the organic separator and organic binder, thereby greatly increasing the metal leaching rate in the subsequent solution leaching process.

[0045] Comparative Example 3:

[0046] First, fully discharge the used ternary lithium battery in 5% NaCl solution, then disassemble the outer shell and separate each component to obtain the positive electrode sheet. Place the positive electrode sheet in a sealed tubular furnace and calcine it under the pyrolysis tail gas atmosphere. Heat it up to 550 °C at a rate of 10 °C / min and calcine for 6 h to obtain a calcined product. Crush the calcined product and sieve it through a 200-mesh sieve to obtain calcined powder and copper-aluminum foil debris. Stir the calcined powder and water at a solid-liquid ratio of 20 g / L and a stirring rate of 300 r / min at room temperature for 12 h, and the lithium leaching rate is 81.53%. Stir the water leaching residue and citric acid at 300 r / min at 90 °C for 80 min, with a citric acid concentration of 0.5 mol / L and a solid-liquid ratio of 20 g / L. After filtration, acid leaching filtrate and filter residue can be obtained. The acid leaching filtrate is rich in nickel, cobalt, and manganese ions, and the nickel, cobalt, and manganese leaching rates are 99.95%, 99.68%, and 99.48% respectively.

[0047] Comparing Example 8 and Comparative Example 3, it can be seen that the inner core of the battery can also achieve or approach the treatment effect of roasting the positive electrode material alone after being roasted with pyrolysis tail gas, further highlighting the superiority of the present invention. There is no need for a complex process of crushing electrode materials and separating electrode sheets, greatly reducing the cost of recovering valuable metals and graphite from used ternary lithium batteries.

[0048] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principles of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A method for recovering valuable materials from waste ternary lithium batteries, characterized in that: The following steps are involved: 1) Pretreatment: Soak the used ternary lithium battery in 5% NaCl solution to fully discharge it, then remove the outer shell to obtain the lithium battery core; 2) Reduction roasting: The lithium battery core is placed in a sealed tube furnace at a temperature of 350-750°C, and is fully reduced and roasted at low temperature in a pyrolysis tail gas atmosphere. The roasting time is 1-6 hours, and the heating rate is 5-30°C / min. The tail gas is collected for the next reduction roasting cycle. The obtained roasted product is crushed and passed through a 200-mesh sieve to obtain roasted powder and copper and aluminum foil scraps; 3) Water leaching: the calcined powder obtained in step 2) is fully mixed with water at room temperature by mechanical stirring, and leached, and a filtrate and a filter residue are obtained by filtering, and the filter residue is then washed and dried to obtain a water leaching residue; 4) Acid leaching: The water leaching residue obtained in step 3) is fully mixed with the acid solution by mechanical stirring, and leached. After filtering, a filtrate and a filter residue can be obtained. The filter residue is then washed and dried to obtain an acid leaching residue. The main component of the acid leaching residue is graphite, and the filtrate is rich in nickel, cobalt, and manganese ions. The filtrate and the acid leaching residue are further recovered and purified.

2. The method according to claim 1, characterized in that Step 2) Reduction Calcination: In a sealed tube furnace, the temperature is 450-650° C., and sufficient low-temperature reduction calcination is carried out in the atmosphere of pyrolysis tail gas. The calcination time is 5-6 hours, and the heating rate is 5-20° C. / min.

3. The method according to claim 1, characterized in that In step 3), the mechanical stirring rate is 200-500 r / min, the solid-liquid ratio during the water immersion process is 10-50 g / L, and the water immersion time is 6-12 h.

4. The method according to claim 1, characterized in that: In step 3), the mechanical stirring rate is 300-500 r / min, the solid-liquid ratio during the water immersion process is 10-30 g / L, and the water immersion time is 10-12 h.

5. The method according to claim 1, characterized in that Step 3) The water filtrate is distilled under reduced pressure to obtain Li2CO3.

6. The method according to claim 1, characterized in that The acid in step 4) is one of sulfuric acid, citric acid and p-toluenesulfonic acid.

7. The method according to claim 1, characterized in that In step 4), the acid concentration is 0.1-1.0 mol / L.

8. The method according to claim 1, characterized in that In step 4), the mechanical stirring rate is 200-500 r / min, the solid-liquid ratio during the acid leaching process is 10-50 g / L, the acid leaching temperature is 50-90° C., and the acid leaching time is 60-120 min.

9. The method according to claim 1, characterized in that: In step 4), the acid leaching temperature is 70-90°C.

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