Method for recovering cobalt chloride hexahydrate from waste lithium battery positive electrode material

Abstract

The application relates to the technical field of lithium battery recycling, and specifically discloses a method for recycling cobalt chloride hexahydrate from positive electrode materials of waste lithium batteries, which comprises the following steps: pre-removing aluminum, acid dissolving, chemically removing impurities, extracting and removing impurities, extracting and separating, and concentrating and crystallizing; the specific process of the acid dissolving is as follows: first, dilute sulfuric acid is used to dissolve the wet cobalt residue obtained by pre-removing aluminum to obtain a first liquid and a first waste residue; then, concentrated sulfuric acid is used to dissolve the first waste residue to obtain a second liquid and a second waste residue; the first liquid is directly concentrated to obtain a cobalt sulfate concentrated solution; the second liquid is used to dissolve new wet cobalt residue to realize recycling; and the second waste residue is treated and used as solid waste. The acid dissolving step is optimized, the method of multiple acidification is adopted, the loss rate of cobalt is reduced, the recycling of acid liquid is realized, and pollution discharge is reduced. Meanwhile, the acid dissolving step does not need to use sulfur dioxide, which is conducive to controlling the environmental pollution risk.

Description

Technical Field

[0001] This application relates to the field of lithium battery recycling, and more specifically, it relates to a method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials. Background Technology

[0002] With the widespread use of lithium-ion batteries, the large number of discarded lithium batteries, if not disposed of in a timely manner, will lead to serious environmental pollution and resource waste. Therefore, how to rationally recycle lithium batteries is a problem of widespread concern both domestically and internationally.

[0003] Nickel and cobalt resources in the cathode materials of spent lithium-ion batteries have high recycling value, but they contain many types and high amounts of impurities. Hydrometallurgical methods are commonly used for nickel and cobalt resource recovery, and the specific recycling process includes the following steps: alkaline dissolution, acid dissolution, chemical removal of iron and aluminum, extraction for impurity removal, and nickel-cobalt extraction separation. Specifically, Chinese patent CN104577247A discloses a process for recovering cobalt chloride from spent lithium-ion batteries. Based on the above recycling process, the cobalt-containing solution obtained from the extraction separation is back-extracted, concentrated, and crystallized to obtain cobalt chloride hexahydrate.

[0004] The traditional acid dissolution step is as follows: A certain amount of water is added to the acid dissolution vessel, followed by wet cobalt material. 98% sulfuric acid and extraction regeneration acid are added to adjust the pH of the reaction solution to 0.5. Steam is then introduced for direct heating, raising the temperature of the acid dissolution vessel to 80-85°C and maintaining this temperature for approximately 5-7 hours. Simultaneously, a small amount of sulfur dioxide is introduced to reduce the trivalent cobalt in the wet cobalt slag to a divalent state. Because sulfur dioxide is used in the process, sulfur dioxide cylinders are stored in the plant. If a leak occurs, sulfur dioxide will enter the atmosphere, causing pollution and posing an environmental risk. Summary of the Invention

[0005] To reduce the environmental pollution risk caused by sulfur dioxide, this application provides a method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials.

[0006] This application provides a method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials, employing the following technical solution:

[0007] A method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials includes the following steps: pre-aluminum removal, acid dissolution, chemical impurity removal, extraction impurity removal, extraction separation, and concentration crystallization.

[0008] The specific process of acid dissolution is as follows: First, the wet cobalt slag obtained after pre-aluminum removal is dissolved with dilute sulfuric acid to obtain the first liquid and the first waste residue. Then, the first waste residue is dissolved with concentrated sulfuric acid to obtain the second liquid and the second waste residue. The first liquid is directly concentrated to obtain cobalt sulfate concentrate. The second liquid is used to dissolve new wet cobalt slag to achieve recycling. The second waste residue is treated as solid waste.

[0009] By adopting the above technical solution and optimizing the acid dissolution step, insoluble substances such as graphite and plastic particles in the wet cobalt slag are first dissolved with dilute sulfuric acid, and then cobalt is extracted by dissolving with concentrated sulfuric acid. This multiple acidification process reduces the cobalt loss rate and enables the recycling of acid, thereby reducing pollution emissions. Furthermore, the acid dissolution step eliminates the need for sulfur dioxide, which helps control environmental pollution risks.

[0010] Optionally, the specific process of pre-aluminum removal is as follows: the sheet-like lithium cobalt paper is crushed, then an alkaline solution is added, and after the alkaline dissolution is completed, it is filtered and washed with water to obtain wet cobalt slag.

[0011] By employing the above technical solution, approximately 65% ​​of the aluminum is dissolved by sodium hydroxide during the alkaline dissolution process, while fine powders of carbon black and a small amount of lithium cobalt are lost during the alkaline dissolution and washing processes. Using alkaline dissolution to reduce the aluminum content can decrease the processing load on subsequent chemical purification processes.

[0012] Optionally, the specific process of chemical purification is as follows: First, heat the concentrated cobalt sulfate solution obtained by acid dissolution to 60-70℃, add sodium chlorate, and continue for 20-40 minutes. Then, raise the temperature to 80-90℃, control the pH at 1.5-2, and react for 2-4 hours to precipitate iron ions as yellow sodium alum. Then, filter to obtain the solution. Finally, adjust the pH of the solution to 4 to hydrolyze iron ions and aluminum ions to form precipitates. After filtration again, obtain a cobalt-containing solution.

[0013] By adopting the above technical solution, the cobalt sulfate concentrate obtained by acid dissolution still contains a large amount of aluminum and iron ions. First, sodium chlorate is used to oxidize ferrous iron to ferric iron, and the pH is controlled at 1.5-2, so that iron ions can easily form yellow sodium iron alum precipitate, thereby significantly reducing the content of iron and aluminum.

[0014] Optionally, the specific process of extraction and impurity removal is as follows: after mixing and saponifying P204 extractant and alkali solution, it is mixed with cobalt-containing solution obtained by chemical impurity removal. After extraction, the first aqueous phase and the first oil phase are separated. The first aqueous phase is the nickel-cobalt solution, which is then introduced into the next process.

[0015] By adopting the above technical solution, since the solution contains a large number of metal ions such as manganese and copper, they are easy to combine with the P507 extractant used in the extraction and separation, resulting in low product purity. Therefore, the P204 extractant is first used for extraction and impurity removal to reduce the concentration of metal ions such as iron, manganese, aluminum and copper, which is beneficial to improve the purity of cobalt chloride products.

[0016] Optionally, in the specific process of extraction and impurity removal, the first oil phase is washed with 10wt% sulfuric acid, the acid solution generated from the washing is mixed with the first aqueous phase, and the washed first oil phase is washed sequentially with 20wt% sulfuric acid and 15wt% hydrochloric acid to complete the regeneration of the extractant.

[0017] By adopting the above technical solution, on the one hand, washing with 10wt% sulfuric acid can improve the recovery rate of cobalt and prevent a small amount of cobalt from being trapped in the first oil phase; on the other hand, the extractant can be recycled, which helps to reduce costs.

[0018] Optionally, the P204 extractant comprises the following components in parts by weight: 20-30 parts P204, 70-80 parts sulfonated kerosene, and 6-8 parts octanoyl hydroxamic acid.

[0019] By adopting the above technical solution, octanoyl hydroxamic acid is added to the traditional P204 extractant to meet the complex scenario of lithium cobalt paper with many types and high content of impurities. Among them, octanoyl hydroxamic acid has the ability to selectively chelate metals, and in particular, it has a strong coordination effect on aluminum during the extraction and impurity removal process, thereby effectively reducing the aluminum content and improving the purity of the product.

[0020] Optionally, the P204 extractant may also include 2-3 parts of catechins.

[0021] By adopting the above technical solution, catechins exhibit strong selectivity for iron, effectively reducing iron content and improving product purity during the extraction and impurity removal process.

[0022] Optionally, the nickel-cobalt solution obtained from the extraction and impurity removal is diluted to Co ≤ 15 g / L before entering the extraction and separation step.

[0023] The above technical solutions are adopted to improve the extraction and separation effect.

[0024] Optionally, the specific process of extraction and separation is as follows: P507 extractant is mixed with alkali solution and saponified, and then mixed with nickel-cobalt solution obtained by extraction and impurity removal. P507 extractant includes 25wt% P507 and 75wt% sulfonated kerosene. After extraction, a second aqueous phase and a second oil phase are separated. The second oil phase is first washed with 10wt% sulfuric acid and then back-extracted with 20wt% hydrochloric acid to obtain cobalt chloride solution.

[0025] By adopting the above technical solution, the second oil phase is washed with 10wt% sulfuric acid to remove the small amount of Ni ions trapped in the oil phase and improve the purity of the product.

[0026] Optionally, the specific process of concentration and crystallization is as follows: the cobalt chloride solution obtained by extraction and separation is evaporated and concentrated to precipitate cobalt chloride, and finally cobalt chloride hexahydrate is obtained by centrifugation.

[0027] In summary, this application has the following beneficial effects:

[0028] 1. This application optimizes the overall recycling process and adjusts the formula of P204 extractant to effectively improve the impurity removal effect and ensure the purity of cobalt chloride hexahydrate product;

[0029] 2. In the acid dissolution step of this application, the use of multiple acidification methods can reduce the loss rate of cobalt and realize the recycling of acid solution, thereby reducing pollution emissions; at the same time, the acid dissolution step does not require the use of sulfur dioxide, which is beneficial to controlling the risk of environmental pollution. Detailed Implementation

[0030] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0031] The embodiments of this application use the following raw materials:

[0032] Lithium cobalt paper, also known as lithium cobalt material or cobalt waste, refers to the positive electrode material from scrapped or used lithium batteries after stripping and screening. It is shaped like a piece of black paper and has a high cobalt content, usually above 43%. The content of various impurities is effectively controlled during the production of battery raw materials such as lithium cobalt oxide, and is generally below 0.2%. The content of lead, mercury, cadmium and chromium, the four metals restricted by the EU RoHS directive, is all less than 0.0005%.

[0033] Based on the analysis of the forms in which the various metals exist in the lithium cobalt material, cobalt mainly exists in the form of lithium cobalt oxide, manganese mainly exists in the form of lithium manganese oxide, nickel mainly exists in the form of lithium nickel oxide, aluminum mainly exists in the form of aluminum foil, and iron and manganese, as positive electrode materials, were not completely separated during the stripping process and remained in the lithium cobalt material in small quantities.

[0034] Specifically, the composition of the lithium cobalt paper used in this application embodiment is shown in Table 1:

[0035] Table 1. Composition of Lithium Cobalt Paper

[0036] Element Co Al Li O Fe Mn Cu Ni other Content (wt%) 43 10 5.1 31 0.5 1 0.6 3 5.8

[0037] Note: Others mainly include plastic parts, carbon black, etc.

[0038] The reaction equations involved in the embodiments of this application are as follows:

[0039] (1) Pre-aluminum removal:

[0040] 2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂

[0041] 2NaAlO2+H2SO4+2H2O→2Al(OH)3↓+Na2SO4

[0042] (2) Acid solubility:

[0043] 4LiCoO2+6H2SO4→2Li2SO4+4CoSO4+6H2O+O2

[0044] 2Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂

[0045] 4LiMnO2+6H2SO4→2Li2SO4+4MnSO4+6H2O+O2

[0046] 4LiNiO2+6H2SO4→2Li2SO4+4NiSO4+6H2O+O2

[0047] 2Fe + 3H₂SO₄ → Fe₂(SO₄)₃ + 3H₂

[0048] (3) Chemical purification:

[0049] 6Fe 2+ +ClO3 - +6H + →6Fe 3+ +Cl - +3H 2 0

[0050] 3Fe2(SO4)3+Na2SO4+12H2O→Na2Fe6(SO4)4(OH) 12 +6H2SO4

[0051] Example 1:

[0052] A method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials includes the following steps:

[0053] (1) Pre-aluminum removal: The sheet-like lithium cobalt paper is crushed by a crushing device and added to the alkaline dissolution tank along with 20wt% alkaline solution. The mixture is stirred for 6 hours to allow sodium hydroxide and aluminum to react, thereby reducing the aluminum content in the lithium cobalt material. After the waste alkaline solution is discharged from the bottom of the alkaline dissolution tank, rinsing water is added for 3 rinses to obtain wet cobalt slag.

[0054] Sulfuric acid is added to the waste alkaline solution for pretreatment, and aluminum hydroxide is produced by reaction. After being filtered by a filter press, the aluminum hydroxide can be sold as a by-product, reducing the amount of hazardous solid waste generated.

[0055] (2) Acid dissolution: First, the wet cobalt slag obtained after pre-aluminum removal is dissolved in 3mol / L dilute sulfuric acid, filtered to obtain the first liquid and the first waste residue. Then, the first waste residue is dissolved in 10mol / L concentrated sulfuric acid, filtered to obtain the second liquid and the second waste residue. The first liquid is directly concentrated to obtain cobalt sulfate concentrate. The second liquid is used to dissolve new wet cobalt slag to achieve recycling. The second waste residue is treated as solid waste.

[0056] (3) Chemical purification: First, heat the cobalt sulfate concentrate obtained by acid dissolution to 60°C, add sodium chlorate, and continue for 20 minutes to oxidize ferrous iron to ferric iron. Then, raise the temperature to 80°C, control the pH at 1.5, and react for 2 hours to precipitate iron ions as yellow sodium alum. Then, filter the solution through a filter press to obtain the feed liquid. After the filter residue is slurried, it is put back into the filter press. Then, these filter residues are slurried again and put into the filter press. The pH is achieved by washing with water. The high-pressure air pump on the filter press dries the filter residue to reduce the moisture. The filtered solution may not have completely removed iron and may also contain aluminum that has not fully reacted in the alkali dissolution. Therefore, the pH is adjusted to 4 again to hydrolyze iron ions and aluminum ions to form precipitates. After filtration again, a cobalt-containing solution is obtained.

[0057] (4) Extraction and purification: P204 extractant and 30wt% alkaline solution are mixed and saponified, and then put into the extraction tank with an oil-water mass ratio of 1:2. It is mixed with the cobalt-containing solution obtained by chemical purification. Metal ions such as Cu, Mn, and Zn are adsorbed into the organic phase by the extractant, while the unextracted Co and Ni metal ions remain in the aqueous phase. After extraction, the first aqueous phase and the first oil phase are separated. The first aqueous phase is the nickel-cobalt solution. After further separation from the oil phase in the aqueous phase clarification tank, it is diluted. The Co content is reduced to 15g / L before entering the extraction and separation step.

[0058] The P204 extractant comprises the following components in the following mass ratio: 25 wt% P204 and 75 wt% sulfonated kerosene;

[0059] The first oil phase enters the washing tank. To prevent the oil phase from being entrained with small amounts of cobalt and to improve the cobalt recovery rate, it is washed with 10wt% sulfuric acid. The acid produced during washing also enters the aqueous phase clarification tank and mixes with the first aqueous phase. The oil phase produced during washing then continues to enter the impurity washing tank and the regeneration tank. Both the impurity washing tank and the regeneration tank serve to regenerate the extractant. First, the oil phase is washed in the impurity washing tank with 20wt% sulfuric acid, so that most of the metal ions adsorbed by the extractant are washed into the acid solution. Then, it enters the regeneration tank where 15wt% hydrochloric acid is added to remove the more difficult-to-remove Fe adsorbed in the extractant. 3+This process regenerates the extractant. The waste sulfuric acid produced during washing is sent to the wastewater treatment unit, and the waste hydrochloric acid produced during extraction and regeneration can be reused in the acid dissolution process.

[0060] (5) Extraction and separation: P507 extractant is mixed with 30wt% alkaline solution and then saponified. The mixture is then introduced into the extraction tank with an oil-to-water mass ratio of 1:1.5. It is mixed with the nickel-cobalt solution obtained after extraction and impurity removal. Co ions are adsorbed into the oil phase by P507 extractant, while unextracted Ni ions remain in the aqueous phase. After extraction, the second aqueous phase and the second oil phase are separated. The second aqueous phase enters the aqueous phase clarification tank and is further separated from the oil phase before entering the nickel precipitation process.

[0061] The second oil phase enters the washing tank and is washed with 10wt% sulfuric acid to remove a small amount of Ni ions. It then continues to enter the back-extraction tank, where 20wt% hydrochloric acid is added for back-extraction, allowing the Co ions in the oil phase to enter the aqueous phase, resulting in a cobalt chloride solution.

[0062] The oil phase after back-extraction is then fed into a regeneration tank where 15wt% hydrochloric acid is added to regenerate the extractant. The waste hydrochloric acid generated during extraction and regeneration is recycled for the acid dissolution process.

[0063] The P507 extractant consists of 25 wt% P507 and 75 wt% sulfonated kerosene;

[0064] (6) Concentration and crystallization: The cobalt chloride solution obtained after extraction and separation is put into the concentration kettle for evaporation and concentration. After the water in the solution is evaporated and a saturated solution is formed, it is put into the crystallization kettle. After the indirect cooling water is introduced to cool down, cobalt chloride precipitates out of the solution. Finally, the cobalt chloride hexahydrate product is obtained by centrifugation. The mother liquor obtained by separation is returned to the concentration kettle and concentrated and crystallized again with a new cobalt chloride solution.

[0065] Example 2:

[0066] The difference from Example 1 is that the chemical impurity removal process parameters are different.

[0067] Specifically, (3) Chemical purification: First, heat the concentrated cobalt sulfate solution obtained by acid dissolution to 65°C, add sodium chlorate, and continue for 30 minutes to oxidize ferrous iron to ferric iron. Then, raise the temperature to 85°C, control the pH at 1.8, and react for 3 hours to precipitate iron ions as yellow sodium alum. Then, filter the solution through a filter press to obtain the feed liquid. After the filter residue is slurried, it is put back into the filter press. Then, these filter residues are slurried again and put into the filter press. The pH is achieved by washing with water. The high-pressure air pump on the filter press dries the filter residue to reduce the moisture. The filtered solution may not have completely removed iron and may also contain aluminum that has not fully reacted in the alkali dissolution. Therefore, adjust the pH to 4 again to hydrolyze iron ions and aluminum ions to form precipitates. After filtration again, a cobalt-containing solution is obtained.

[0068] Example 3:

[0069] The difference from Example 1 is that the chemical impurity removal process parameters are different.

[0070] Specifically, (3) Chemical purification: First, heat the concentrated cobalt sulfate solution obtained by acid dissolution to 70°C, add sodium chlorate, and continue for 40 minutes to oxidize ferrous iron to ferric iron. Then, raise the temperature to 90°C, control the pH at 2, and react for 4 hours to precipitate iron ions as yellow sodium ferric alum. Then, filter the solution through a filter press to obtain the feed liquid. After the filter residue is slurried, it is reintroduced into the filter press. Then, these filter residues are slurried again and reintroduced into the filter press. The pH is achieved by washing with water. The high-pressure air pump on the filter press dries the filter residue to reduce the moisture. The filtered solution may not have completely removed iron and may also contain aluminum that has not fully reacted in the alkali dissolution. Therefore, adjust the pH to 4 again to hydrolyze iron ions and aluminum ions to form precipitates. After filtration again, a cobalt-containing solution is obtained.

[0071] Example 4:

[0072] The difference from Example 1 is that the chemical purification process is different.

[0073] Specifically, (3) Chemical purification: Sodium chlorate is added to the cobalt sulfate concentrate, and steam is introduced for direct heating to raise the temperature of the reaction solution to 80°C. At the same time, 20wt% sodium carbonate solution is added. Under the neutralization reaction of sodium carbonate, the pH value of the reaction solution is controlled to 4.0 for 4 hours.

[0074] Example 5:

[0075] The difference from Example 1 is that the components of the P204 extractant are different.

[0076] The P204 extractant comprises the following components in parts by weight: 20 parts P204, 70 parts sulfonated kerosene, and 6 parts octanoyl hydroxamic acid.

[0077] Example 6:

[0078] The difference from Example 1 is that the components of the P204 extractant are different.

[0079] The P204 extractant comprises the following components in parts by weight: 30 parts P204, 80 parts sulfonated kerosene, and 8 parts octanoyl hydroxamic acid.

[0080] Example 7:

[0081] The difference from Example 1 is that the components of the P204 extractant are different.

[0082] The P204 extractant comprises the following components in parts by weight: 25 parts P204, 75 parts sulfonated kerosene, and 7 parts octanoyl hydroxamic acid.

[0083] Example 8:

[0084] The difference from Example 7 is that the P204 extractant also includes 2 parts of catechin.

[0085] Example 9:

[0086] The difference from Example 7 is that the P204 extractant also includes 3 parts of catechin.

[0087] Impurity metal detection:

[0088] The cobalt-containing solutions in Examples 1-4, after chemical purification, were tested to determine their iron and aluminum ion concentrations. The results are shown in Table 2.

[0089] Table 2. Impurity Metal Content of Cobalt-Containing Solutions

[0090] Iron (mg / L) Aluminum (mg / L) Example 1 4.9 5.6 Example 2 4.5 5.5 Example 3 4.4 5.5 Example 4 8.7 6.1

[0091] As shown in Table 2, the iron ion content in Examples 1-3 is significantly lower than that in Example 4. This indicates that controlling the pH within a suitable range is beneficial for the formation of sodium ferric sulfate precipitate and the removal of iron ions.

[0092] The nickel-cobalt solutions after extraction and impurity removal in Examples 1-3 and Examples 5-9 were tested to determine the ion concentrations of aluminum, iron, manganese, and copper. The results are shown in Table 3.

[0093] Table 3. Impurity Metal Content of Nickel-Cobalt Solution

[0094] Iron (mg / L) Aluminum (mg / L) Manganese (mg / L) Copper (mg / L) Example 1 2.5 2.9 2.3 1.7 Example 2 2.6 3.1 2.1 1.8 Example 3 2.3 2.8 2.1 2.0 Example 5 2.3 1.7 1.9 1.7 Example 6 2.2 1.5 1.8 1.5 Example 7 2.4 1.5 1.9 1.7 Example 8 1.5 1.5 1.9 1.6 Example 9 1.3 1.6 1.8 1.6

[0095] As shown in Table 3, the average aluminum ion content of Examples 5-7 was significantly lower than that of Examples 1-3, and the average iron ion content of Examples 8 and 9 was significantly lower than that of Example 7. This indicates that the addition of octanoyl hydroxamic acid and catechin is beneficial for further removing impurity metals and improving product purity.

[0096] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials, characterized in that, The process includes the following steps: pre-aluminum removal, acid dissolution, chemical impurity removal, extraction impurity removal, extraction separation, and concentration crystallization; The specific process of acid dissolution is as follows: First, the wet cobalt slag obtained after pre-aluminum removal is dissolved with dilute sulfuric acid to obtain the first liquid and the first waste residue. Then, the first waste residue is dissolved with concentrated sulfuric acid to obtain the second liquid and the second waste residue. The first liquid is directly concentrated to obtain cobalt sulfate concentrate. The second liquid is used to dissolve new wet cobalt slag to achieve recycling. The second waste residue is treated as solid waste. The specific process of extraction and impurity removal is as follows: P204 extractant and alkali solution are mixed and saponified, and then mixed with cobalt-containing solution obtained by chemical impurity removal. After extraction, the first aqueous phase and the first oil phase are separated. The first aqueous phase is the nickel-cobalt solution, which enters the next process. In the specific process of extraction and impurity removal, the first oil phase is washed with 10wt% sulfuric acid, and the acid solution generated from the washing is mixed with the first aqueous phase. The washed first oil phase is then washed sequentially with 20wt% sulfuric acid and 15wt% hydrochloric acid to complete the regeneration of the extractant. The P204 extractant comprises the following components in parts by weight: 20-30 parts P204, 70-80 parts sulfonated kerosene, 6-8 parts octanoyl hydroxamic acid, and 2-3 parts catechin; The nickel-cobalt solution obtained from the extraction and impurity removal is diluted to Co≤15g / L before entering the extraction and separation step.

2. The method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials according to claim 1, characterized in that: The specific process of pre-aluminum removal is as follows: the sheet-like lithium cobalt paper is crushed, then an alkaline solution is added. After the alkaline dissolution is completed, the mixture is filtered and washed with water to obtain wet cobalt slag.

3. A method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials according to claim 1, characterized in that: The specific process of chemical purification is as follows: First, the concentrated cobalt sulfate solution obtained by acid dissolution is heated to 60-70℃, sodium chlorate is added, and the reaction is continued for 20-40 minutes. Then, the temperature is raised to 80-90℃, the pH is controlled at 1.5-2, and the reaction is carried out for 2-4 hours to precipitate iron ions as yellow sodium alum. Then, the solution is filtered to obtain the feed solution. Finally, the pH of the feed solution is adjusted to 4 to hydrolyze iron ions and aluminum ions to form precipitates. After filtration again, a cobalt-containing solution is obtained.

4. The method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials according to claim 1, characterized in that: The specific extraction and separation process is as follows: P507 extractant is mixed with alkali solution and saponified, and then mixed with nickel-cobalt solution obtained after extraction and impurity removal. P507 extractant includes 25wt% P507 and 75wt% sulfonated kerosene. After extraction, a second aqueous phase and a second oil phase are separated. The second oil phase is first washed with 10wt% sulfuric acid and then back-extracted with 20wt% hydrochloric acid to obtain cobalt chloride solution.

5. The method for recovering cobalt chloride hexahydrate from waste lithium battery cathode materials according to claim 1, characterized in that: The specific process of concentration and crystallization is as follows: the cobalt chloride solution obtained by extraction and separation is evaporated and concentrated to precipitate cobalt chloride, and finally cobalt chloride hexahydrate is obtained by centrifugation.