Method for producing cobalt oxide by recycling waste lithium batteries and recycling mother liquor in production process

Abstract

The invention relates to the technical field of lithium battery recovery, in particular to a method for producing cobalt oxide by recovering waste lithium batteries and recycling mother liquor in the production process. Comprising the following steps of lithium cobalt oxide battery disassembly and pretreatment, valuable metal leaching, extraction separation, hydroxyl cobalt oxide production and mother liquor recycling treatment. Citric acid and hydrogen peroxide are used as valuable metal leaching agents, efficient leaching of valuable metal such as lithium and cobalt can be achieved, dependence on strong acid is reduced, and safety risks and environmental pollution in the recovery process are reduced. The cobalt sulfate solution obtained by recycling the waste lithium cobalt oxide batteries is used for producing and preparing the hydroxyl cobalt oxide, after the hydroxyl cobalt oxide is obtained, the residual mother liquor contains a sodium hydroxide component, the mother liquor is subjected to impurity removal treatment, the recyclable alkali liquor can be obtained, the recyclable alkali liquor can be used as saponification liquid alkali to be used in the extraction separation step, resource waste is reduced, and the resource utilization rate is increased. The resource recycling rate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery recycling, and more specifically, to a method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process. Background Art

[0002] The recycling of waste lithium batteries is an important environmental protection and resource recycling process. By extracting valuable materials such as cobalt, lithium, nickel, etc. from waste lithium batteries, it can not only effectively reduce environmental pollution, but also maximize the utilization of resources.

[0003] The wet leaching process has attracted much attention in the recovery of valuable metals from waste lithium batteries due to its advantages such as high efficiency, low cost and relatively light pollution. Wet recovery technology covers multiple steps such as pretreatment, leaching, element separation and extraction, and material regeneration. In the leaching treatment stage of wet recovery, strong inorganic acids (such as ammonium sulfate, sulfuric acid, etc.) are often used to leach electrode powder so that valuable metals enter the solution in the form of ions. However, due to their strong corrosiveness and strong oxidizing properties, strong inorganic acids may cause environmental pollution, equipment corrosion, and safety hazards during use. In order to overcome these defects, it is necessary to further explore and develop an environmentally friendly and safer valuable metal leaching method and process.

[0004] In addition, lithium cobalt oxide is the most widely used positive electrode active material in the preparation of lithium batteries, and one of its raw materials is cobalt hydroxide oxide. In the process of recycling cobalt hydroxide oxide from waste lithium batteries, the saponification treatment before cobalt extraction and separation and the precipitation generation operation of cobalt hydroxide oxide preparation will involve the addition and use of alkaline solution. This not only leads to a large amount of alkaline solution, which is easy to cause waste of resources and cost increase, but also produces a large amount of alkaline waste liquid, further increasing the cost of waste liquid treatment and the risk of environmental pollution. Therefore, we urgently need to develop methods and processes that can not only ensure the normal production of cobalt hydroxide oxide from waste lithium batteries, but also improve the utilization rate of alkaline solution, achieve effective reuse of alkaline solution, and reduce resource waste. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process.

[0006] The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process comprises the following steps: S1: Disassembly and pretreatment of lithium cobalt oxide batteries: discharge and disassemble the lithium cobalt oxide batteries, and obtain positive electrode material powder after shelling, crushing and screening. The positive electrode material powder is roasted, alkaline leached and filtered to obtain alkaline leached positive electrode material powder; S2: leaching of valuable metals, mixing the positive electrode material powder after alkali leaching with citric acid solution and hydrogen peroxide solution for ball milling reaction, filtering to obtain a leachate and filter residue; S3: extraction and separation, using sodium hydroxide solution to saponify the di(2-ethylhexyl) phosphate solution and the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution, respectively, to obtain organic extractant A and organic extractant B, and sequentially using organic extractant A and organic extractant B to extract and separate Co in the leachate, and back-extracting with sulfuric acid solution to obtain a cobalt sulfate solution; S4: producing cobalt hydroxide oxide and recycling mother liquor, flowing sodium hydroxide solution and cobalt sulfate solution obtained in step S3 into the reactor at the same time, heating and continuously stirring the reaction under alkaline conditions, and continuously injecting oxygen. After the stirring reaction is completed, filtering to obtain precipitate and mother liquor, washing and drying the precipitate to obtain cobalt hydroxide oxide, using barium hydroxide solution to remove impurities from the mother liquor until the white precipitate no longer increases, filtering to obtain reusable alkaline solution.

[0007] Optionally, step S1: disassembly and pretreatment of lithium cobalt oxide batteries, comprising the following steps: S1.1: Discharge and disassemble the lithium cobalt oxide battery to separate the positive electrode material, negative electrode material, separator and electrolyte; S1.2: Shelling, crushing and screening the positive electrode material to obtain positive electrode material powder; S1.3: placing the positive electrode material powder in a muffle furnace for roasting, cooling and collecting after the roasting, to obtain the positive electrode material powder; S1.4: Add the positive electrode material powder to a sodium hydroxide solution with a mass fraction of 1% according to a solid-liquid ratio (1-3):10 for alkaline leaching to remove the residual aluminum in the positive electrode material powder. After the alkaline leaching, filter to obtain the alkaline-leached positive electrode material powder.

[0008] Optionally, step S2: valuable metal leaching, specifically comprises the following steps: S2.1: Add the alkaline-leached cathode material powder into a ball mill, and then add a 0.4-1 mol / L citric acid solution and a 10-20% mass fraction hydrogen peroxide solution in sequence, and perform ball milling reaction at 50-80°C for 0.5-2h at a ball milling speed of 60-90rpm; S2.2: After the ball milling is completed, the material in the ball mill tank is poured out and filtered to obtain the leaching liquid and filter residue.

[0009] Optionally, the solid-liquid mass ratio of the positive electrode material powder after alkaline leaching to the citric acid solution and the hydrogen peroxide solution is (1-2): (2-5): (2-5).

[0010] Optionally, step S3: extraction and separation, specifically comprises the following steps: S3.1: diluting di(2-ethylhexyl) phosphate with kerosene to obtain a di(2-ethylhexyl) phosphate solution with a volume concentration of 15-25%, saponifying the di(2-ethylhexyl) phosphate solution with a mass fraction of 20-40% sodium hydroxide solution, wherein the volume ratio of the di(2-ethylhexyl) phosphate solution to the sodium hydroxide solution is (1-2):1, and the saponification rate is controlled at 30-60%, thereby obtaining an organic extractant A; S3.2: using kerosene to dilute 2-ethylhexyl phosphate mono-2-ethylhexyl ester to obtain a 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution having a volume concentration of 15-25%, and saponifying the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a sodium hydroxide solution having a mass fraction of 20-40%, wherein the volume ratio of the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution to the sodium hydroxide solution is (1-2):1, and the saponification rate is controlled at 50-70%, thereby obtaining an organic extractant B; S3.3: adding an organic extractant A to the leachate so that the Cu, Mn, and Fe impurities in the leachate are extracted into the organic extractant A, thereby removing the Cu, Mn, and Fe impurities, while Li and Co remain in the aqueous solution; subsequently, separating and conducting the aqueous solution with Li and Co remaining, and adding an organic extractant B to the aqueous solution so that the Co in the aqueous solution is extracted into the organic extractant B, while Li continues to remain in the aqueous solution; S3.4: Separate and extract the organic extractant B that has been extracted with Co, add sulfuric acid solution to the organic extractant B that has been extracted with Co for back extraction to obtain a cobalt sulfate solution.

[0011] Optionally, the volume ratio of the organic extractant A to the leaching solution is (1-3):1.

[0012] Optionally, the volume ratio of the organic extractant B to the aqueous solution is (1-3):1.

[0013] Optionally, step S4: producing cobalt oxyhydroxide and recycling the mother liquor, specifically comprises the following steps: S4.1: A sodium hydroxide solution having a mass fraction of 30 to 40% and the cobalt sulfate solution obtained in step S3.3 are simultaneously flowed into the reactor, so that the pH value of the liquid in the reactor is controlled at 10.4 to 12, and the reaction is continuously stirred at 60 to 90° C., while oxygen is continuously injected until the cobalt sulfate solution no longer flows into the reactor, and the reaction is continuously stirred for 30 to 50 minutes; S4.2: After the stirring reaction is completed, the reacted material in the reactor is filtered to obtain a precipitate and a mother liquor. The precipitate is washed and dried to obtain cobalt oxyhydroxide; S4.3: Add 0.1 mol / L barium hydroxide solution dropwise to the mother liquor while stirring until the white precipitate no longer increases, and then filter the mother liquor after the reaction to remove the generated white precipitate to obtain reusable alkali solution.

[0014] Optionally, the injection flow rate of oxygen is 10 to 60 L / min.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. In the present invention, citric acid and hydrogen peroxide are used as valuable metal leaching agents to achieve efficient leaching of valuable metals such as lithium and cobalt. Compared with the traditional leaching method using strong inorganic acids (such as sulfuric acid), the valuable metal leaching method using citric acid and hydrogen peroxide is a more environmentally friendly and efficient leaching method, which can effectively improve the metal recovery rate and has less impact on the environment, reducing the dependence on strong acids in the recovery of valuable metals from waste lithium batteries, and reducing the safety risks and environmental pollution in the recovery process.

[0016] 2. In the present invention, the cobalt sulfate solution recovered from waste lithium cobalt oxide batteries is used to produce cobalt hydroxide oxide, which not only effectively extracts and recovers cobalt from waste lithium batteries, but also produces cobalt hydroxide oxide that can be used as a battery additive, thereby increasing resource recovery benefits.

[0017] 3. In the process of producing cobalt hydroxyl oxide, the sodium hydroxide solution is used as a precipitant to create alkaline conditions for the generation of cobalt hydroxyl oxide. After obtaining cobalt hydroxyl oxide, the remaining mother liquor still contains a large amount of sodium hydroxide components. The mother liquor is treated with barium hydroxide to remove impurities, so that the sodium sulfate component doped in the mother liquor can be removed, and the effective concentration of sodium hydroxide in the reusable alkali solution can be increased. The reusable alkali solution can be used as a saponification alkali and then reused in the extraction and separation process, which can improve the extraction and separation effect and ensure the recovery rate of valuable metals. At the same time, the purpose of reducing resource waste and improving resource recovery and utilization rate is achieved. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0019] The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process specifically comprises the following steps: S1: Disassembly and pretreatment of lithium cobalt oxide batteries, S1.1: Discharge and disassemble the lithium cobalt oxide battery to separate the positive electrode material, negative electrode material, separator and electrolyte; S1.2: Shelling, crushing and screening the positive electrode material to obtain positive electrode material powder; S1.3: placing the positive electrode material powder in a muffle furnace for roasting, cooling and collecting after the roasting, to obtain the positive electrode material powder; S1.4: Add the positive electrode material powder to a sodium hydroxide solution with a mass fraction of 1% according to a solid-liquid ratio of 1:10 for alkaline leaching treatment to remove the residual aluminum in the positive electrode material powder. After the alkaline leaching treatment, filter to obtain the positive electrode material powder after alkaline leaching. The content (mass fraction) of some metal components in the positive electrode material powder after alkaline leaching is: 9.33% Li, 56.36% Co, 2.84% Mn, 0.75% Fe, 0.21% Cu; S2: Valuable metal leaching, S2.1: Add the cathode material powder after alkali leaching into a ball mill, and then add a 0.8 mol / L citric acid solution and a 20% mass fraction hydrogen peroxide solution in sequence, and perform ball milling reaction at 60°C for 2 hours at a ball milling speed of 90 rpm, wherein the solid-liquid mass ratio of the cathode material powder after alkali leaching to the citric acid solution and the hydrogen peroxide solution is 1:3:3; S2.2: After the ball milling is completed, the material in the ball mill tank is poured out and filtered to obtain the leaching liquid and filter residue, and the leaching rate of Co is determined. The leaching rate of Co is 98.7%; S3: Extraction and separation, S3.1: diluting di(2-ethylhexyl) phosphate with kerosene to obtain a di(2-ethylhexyl) phosphate solution with a volume concentration of 20%, saponifying the di(2-ethylhexyl) phosphate solution with a mass fraction of 30% sodium hydroxide solution, wherein the volume ratio of the di(2-ethylhexyl) phosphate solution to the sodium hydroxide solution is 2:1, and the saponification rate is controlled at 50%, to obtain an organic extractant A; S3.2: diluting 2-ethylhexyl phosphate mono-2-ethylhexyl ester with kerosene to obtain a 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a volume concentration of 20%, saponifying the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a mass fraction of 30% sodium hydroxide solution, the volume ratio of the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution to the sodium hydroxide solution is 2:1, and the saponification rate is controlled at 60%, to obtain an organic extractant B; S3.3: adding organic extractant A to the leachate, the volume ratio of organic extractant A to the leachate being 3:1, so that Cu, Mn, and Fe impurities in the leachate are extracted into the organic extractant A, thereby removing Cu, Mn, and Fe impurities, while Li and Co remain in the aqueous solution, then separating and deriving the aqueous solution with Li and Co, and adding organic extractant B to the aqueous solution, the volume ratio of organic extractant B to the aqueous solution being 3:1, so that Co in the aqueous solution is extracted into the organic extractant B, while Li continues to remain in the aqueous solution; S3.4: separating and extracting the organic extractant B into which Co has been extracted, adding a sulfuric acid solution to the organic extractant B into which Co has been extracted for stripping, and obtaining a cobalt sulfate solution, wherein the cobalt content of the cobalt sulfate solution is 13.6 g / L, and the recovery rate of cobalt is 98.1%; S4: Production of cobalt oxyhydroxide and mother liquor recycling treatment, S4.1: A sodium hydroxide solution having a mass fraction of 40% and the cobalt sulfate solution obtained in step S3.3 are simultaneously flowed into the reactor, so that the pH value of the liquid in the reactor is controlled at 11.2, and the reaction is continuously stirred at 80° C., and oxygen is continuously injected at a flow rate of 30 L / min until the cobalt sulfate solution no longer flows into the reactor, and the reaction is continuously stirred for 50 min; S4.2: After the stirring reaction is completed, the reacted material in the reactor is filtered to obtain a precipitate and a mother liquor. The precipitate is washed and dried to obtain cobalt oxyhydroxide; S4.3: Add 0.1 mol / L barium hydroxide solution dropwise to the mother liquor while stirring until the white precipitate stops increasing. Filter the mother liquor after the reaction to remove the generated white precipitate to obtain reusable alkali solution. The mass fraction of the reusable alkali solution is determined by neutralization titration method to be 26.4%. Example

[0020] The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process specifically comprises the following steps: S1: Disassembly and pretreatment of lithium cobalt oxide batteries, S1.1: Discharge and disassemble the lithium cobalt oxide battery to separate the positive electrode material, negative electrode material, separator and electrolyte; S1.2: Shelling, crushing and screening the positive electrode material to obtain positive electrode material powder; S1.3: placing the positive electrode material powder in a muffle furnace for roasting, cooling and collecting after the roasting, to obtain the positive electrode material powder; S1.4: Add the positive electrode material powder to a sodium hydroxide solution with a mass fraction of 1% according to a solid-liquid ratio of 1:10 for alkaline leaching treatment to remove the residual aluminum in the positive electrode material powder. After the alkaline leaching treatment, filter to obtain the positive electrode material powder after alkaline leaching. The content (mass fraction) of some metal components in the positive electrode material powder after alkaline leaching is: 8.72% Li, 54.71% Co, 2.63% Mn, 0.45% Fe, 0.06% Cu; S2: Valuable metal leaching, S2.1: Add the cathode material powder after alkali leaching into a ball mill, and then add a 0.8 mol / L citric acid solution and a 20% mass fraction hydrogen peroxide solution in sequence, and perform ball milling reaction at 80°C for 1 hour at a ball milling speed of 60 rpm, wherein the solid-liquid mass ratio of the cathode material powder after alkali leaching to the citric acid solution and the hydrogen peroxide solution is 1:3:3; S2.2: After the ball milling is completed, the material in the ball mill tank is poured out and filtered to obtain the leaching liquid and filter residue, and the leaching rate of Co is determined. The leaching rate of Co is 97.3%; S3: Extraction and separation, S3.1: using kerosene to dilute di(2-ethylhexyl) phosphate to a di(2-ethylhexyl) phosphate solution with a volume concentration of 20%, saponifying the di(2-ethylhexyl) phosphate solution with a mass fraction of 30% sodium hydroxide solution, the volume ratio of the di(2-ethylhexyl) phosphate solution to the sodium hydroxide solution is 2:1, and the saponification rate is controlled at 30%, to obtain an organic extractant A; S3.2: diluting 2-ethylhexyl phosphate mono-2-ethylhexyl ester with kerosene to obtain a 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a volume concentration of 20%, saponifying the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a mass fraction of 30% sodium hydroxide solution, the volume ratio of the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution to the sodium hydroxide solution is 2:1, and the saponification rate is controlled at 50%, to obtain an organic extractant B; S3.3: adding organic extractant A to the leachate, the volume ratio of organic extractant A to the leachate being 3:1, so that Cu, Mn, and Fe impurities in the leachate are extracted into the organic extractant A, thereby removing Cu, Mn, and Fe impurities, while Li and Co remain in the aqueous solution, then separating and deriving the aqueous solution with Li and Co, and adding organic extractant B to the aqueous solution, the volume ratio of organic extractant B to the aqueous solution being 3:1, so that Co in the aqueous solution is extracted into the organic extractant B, while Li continues to remain in the aqueous solution; S3.4: separating and extracting the organic extractant B into which Co has been extracted, adding a sulfuric acid solution to the organic extractant B into which Co has been extracted for stripping, and obtaining a cobalt sulfate solution, wherein the cobalt content of the cobalt sulfate solution is 12.9 g / L, and the recovery rate of cobalt is 96.9%; S4: Production of cobalt oxyhydroxide and mother liquor recycling treatment, S4.1: A sodium hydroxide solution having a mass fraction of 40% and the cobalt sulfate solution obtained in step S3.3 are simultaneously flowed into the reactor, so that the pH value of the liquid in the reactor is controlled at 11.2, and the reaction is continuously stirred at 60° C., and oxygen is continuously injected at a flow rate of 30 L / min until the cobalt sulfate solution no longer flows into the reactor, and the reaction is continuously stirred for 30 min; S4.2: After the stirring reaction is completed, the reacted material in the reactor is filtered to obtain a precipitate and a mother liquor. The precipitate is washed and dried to obtain cobalt oxyhydroxide; S4.3: Add 0.1 mol / L barium hydroxide solution dropwise to the mother liquor while stirring until the white precipitate stops increasing. Filter the mother liquor after the reaction to remove the generated white precipitate to obtain reusable alkali solution. The mass fraction of the reusable alkali solution is determined by neutralization titration to be 27.2%. Example

[0021] The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process specifically comprises the following steps: S1: Disassembly and pretreatment of lithium cobalt oxide batteries, S1.1: Discharge and disassemble the lithium cobalt oxide battery to separate the positive electrode material, negative electrode material, separator and electrolyte; S1.2: Shelling, crushing and screening the positive electrode material to obtain positive electrode material powder; S1.3: placing the positive electrode material powder in a muffle furnace for roasting, cooling and collecting after the roasting, to obtain the positive electrode material powder; S1.4: Add the positive electrode material powder to a sodium hydroxide solution with a mass fraction of 1% according to a solid-liquid ratio of 3:10 for alkaline leaching treatment to remove the residual aluminum in the positive electrode material powder. After the alkaline leaching treatment, filter to obtain the positive electrode material powder after alkaline leaching. The content (mass fraction) of some metal components in the positive electrode material powder after alkaline leaching is: 9.73% Li, 55.79% Co, 2.56% Mn, 0.86% Fe, 0.13% Cu; S2: Valuable metal leaching, S2.1: Add the cathode material powder after alkali leaching into a ball mill, and then add a 0.4 mol / L citric acid solution and a 10% mass fraction hydrogen peroxide solution in sequence, and perform ball milling reaction at 60°C for 2 hours at a ball milling speed of 90 rpm, wherein the solid-liquid mass ratio of the cathode material powder after alkali leaching to the citric acid solution and the hydrogen peroxide solution is 1:5:5; S2.2: After the ball milling is completed, the material in the ball mill tank is poured out and filtered to obtain the leaching liquid and filter residue, and the leaching rate of Co is determined. The leaching rate of Co is 96.6%; S3: Extraction and separation, S3.1: using kerosene to dilute di(2-ethylhexyl) phosphate to a di(2-ethylhexyl) phosphate solution with a volume concentration of 20%, saponifying the di(2-ethylhexyl) phosphate solution with a mass fraction of 30% sodium hydroxide solution, the volume ratio of the di(2-ethylhexyl) phosphate solution to the sodium hydroxide solution is 1:1, and the saponification rate is controlled at 50%, to obtain an organic extractant A; S3.2: diluting 2-ethylhexyl phosphate mono-2-ethylhexyl ester with kerosene to obtain a 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a volume concentration of 20%, saponifying the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a mass fraction of 30% sodium hydroxide solution, the volume ratio of the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution to the sodium hydroxide solution being 1:1, and the saponification rate being controlled at 60%, to obtain an organic extractant B; S3.3: adding an organic extractant A to the leachate, wherein the volume ratio of the organic extractant A to the leachate is 2:1, so that the Cu, Mn, and Fe impurities in the leachate are extracted into the organic extractant A, thereby removing the Cu, Mn, and Fe impurities, while Li and Co remain in the aqueous solution; subsequently, separating and deriving the aqueous solution with Li and Co, and adding an organic extractant B to the aqueous solution, wherein the volume ratio of the organic extractant B to the aqueous solution is 2:1, so that the Co in the aqueous solution is extracted into the organic extractant B, while Li continues to remain in the aqueous solution; S3.4: separating and extracting the organic extractant B into which Co has been extracted, adding a sulfuric acid solution to the organic extractant B into which Co has been extracted for stripping, and obtaining a cobalt sulfate solution, wherein the cobalt content of the cobalt sulfate solution is 12.1 g / L, and the recovery rate of cobalt is 96.1%; S4: Production of cobalt oxyhydroxide and mother liquor recycling treatment, S4.1: A sodium hydroxide solution having a mass fraction of 40% and the cobalt sulfate solution obtained in step S3.3 are simultaneously flowed into the reactor, so that the pH value of the liquid in the reactor is controlled at 12, and the reaction is continuously stirred at 80° C., and oxygen is continuously injected at a flow rate of 50 L / min until the cobalt sulfate solution no longer flows into the reactor, and the reaction is continuously stirred for 50 min; S4.2: After the stirring reaction is completed, the reacted material in the reactor is filtered to obtain a precipitate and a mother liquor. The precipitate is washed and dried to obtain cobalt oxyhydroxide; S4.3: Add 0.1 mol / L barium hydroxide solution dropwise to the mother liquor while stirring until the white precipitate stops increasing. Filter the mother liquor after the reaction to remove the generated white precipitate to obtain reusable alkali solution. The mass fraction of the reusable alkali solution is determined by neutralization titration to be 25.8%.

[0022] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that the citric acid solution and the hydrogen peroxide solution in step S2.1 are replaced with sulfuric acid, and the valuable metal leaching operation is performed on the positive electrode material powder after alkaline leaching using sulfuric acid: Take the positive electrode material powder after alkali leaching with the same composition as in Example 1, add the positive electrode material powder after alkali leaching into a ball mill, and then add a sulfuric acid solution with a mass fraction of 25%. At 80°C, the ball milling reaction was carried out for 1h, and the ball milling speed was 90rpm. The solid-liquid mass ratio of the positive electrode material powder after alkali leaching to the sulfuric acid solution was 1:6. After the ball milling, the material in the ball mill was poured out and filtered to obtain a leachate and a filter residue, and the leaching rate of Co was determined. The leaching rate of Co was 95.4%.

[0023] Combining the cobalt leaching rates of Examples 1-3 and Comparative Example 1, it can be seen that Examples 1-3 use citric acid and hydrogen peroxide as valuable metal leaching agents to achieve efficient leaching of cobalt, and the leaching rate of cobalt can reach more than 96%. Compared with the traditional sulfuric acid leaching method in Comparative Example 1, the effect of leaching cobalt using citric acid and hydrogen peroxide is better, indicating that the valuable metal leaching operation of citric acid and hydrogen peroxide is an environmentally friendly leaching method with a higher metal recovery rate, which is beneficial to reduce dependence on strong acid and reduce safety risks and environmental pollution in the recovery process.

[0024] Comparative Example 2 Compared with Example 1, the difference of Comparative Example 2 is that the reusable alkali solution obtained in Example 1 is reused in the saponification treatment of the extractant, and the specific operation is: using the positive electrode material powder after alkali leaching with the same components as in Example 1, performing the valuable metal leaching operation under the same conditions as step S2 of Example 1, and after obtaining the leachate, the reusable alkali solution obtained in Example 1 is added to the di(2-ethylhexyl) phosphate solution and the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution, respectively, to prepare organic extractant A and organic extractant B, and the organic extractant A and the organic extractant B are used to extract and separate Co in the leachate, and the other steps remain unchanged to prepare a cobalt sulfate solution, the cobalt content of the cobalt sulfate solution is 12.4 g / L, and the cobalt recovery rate is 96.3%.

[0025] Combining the cobalt recovery rate and the mass fraction of the reusable alkali solution of Examples 1-3 and the cobalt recovery rate of Comparative Example 2, it can be seen that in the production and preparation process of cobalt hydroxide oxide in Examples 1-3, the mass fraction of 40% sodium hydroxide solution used can be recovered to obtain a reusable alkali solution with a mass fraction of more than 25% of sodium hydroxide after mother liquor separation, collection, impurity removal and filtration, while in Comparative Example 2, the reusable alkali solution recovered in Example 1 is used for the saponification treatment in the extraction and separation step, and the cobalt recovery rate after the final extraction and separation can also be at the level of 96.3%, indicating that the mother liquor in the production process of cobalt hydroxide oxide can be reused in the extraction and separation process as a saponification liquid alkali after the reuse treatment, which effectively improves resource utilization and reduces resource waste.

[0026] Comparative Example 3 Compared with Example 1, the difference of Comparative Example 3 is that step S4.3 is removed to obtain a mother liquor, and the mass fraction of sodium hydroxide in the mother liquor is determined to be 23.7% by neutralization titration method, and the obtained mother liquor is directly reused in the saponification treatment of the extractant. The specific operation is: using the positive electrode material powder after alkali leaching with the same components as in Example 1, a valuable metal leaching operation is performed under the same conditions as step S2 of Example 1 to obtain a leachate, and the mother liquor obtained in step S4.2 is added to the di(2-ethylhexyl) phosphate solution and the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution, respectively, to prepare organic extractants A and organic extractants B, and organic extractants A and organic extractants B are used to extract and separate Co in the leachate, and the other steps remain unchanged to prepare a cobalt sulfate solution, the cobalt content of the cobalt sulfate solution is 9.7 g / L, and the cobalt recovery rate is 93.8%.

[0027] Combining the cobalt recovery rate and the mass fraction of the reusable alkali solution in Examples 1-3 and the cobalt recovery rate and the mass fraction of sodium hydroxide in the mother liquor in Comparative Example 3, it can be seen that the mass fraction of sodium hydroxide in the mother liquor that has not been subjected to impurity removal treatment is lower than the mass fraction of the reusable alkali solution in Examples 1-3, and then the mother liquor is directly reused in the saponification treatment of the extractant, and the cobalt recovery rate after extraction and separation also decreases. This shows that the mother liquor obtained in the production process of cobalt hydroxide oxide is subjected to impurity removal treatment and then reused in the extraction and separation process as a saponification liquid alkali, which is beneficial to improving the extraction and separation effect.

[0028] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention. Parts not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process, characterized in that: The steps include: S1: Disassembly and pretreatment of lithium cobalt oxide batteries: discharge and disassemble the lithium cobalt oxide batteries, and obtain positive electrode material powder after shelling, crushing and screening. The positive electrode material powder is roasted, alkaline leached and filtered to obtain alkaline leached positive electrode material powder; S2: leaching of valuable metals, mixing the positive electrode material powder after alkali leaching with citric acid solution and hydrogen peroxide solution for ball milling reaction, filtering to obtain a leachate and filter residue; S3: extraction and separation, using sodium hydroxide solution to saponify the di(2-ethylhexyl) phosphate solution and the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution, respectively, to obtain organic extractant A and organic extractant B, and sequentially using organic extractant A and organic extractant B to extract and separate Co in the leachate, and back-extracting with sulfuric acid solution to obtain a cobalt sulfate solution; S4: producing cobalt hydroxide oxide and recycling mother liquor, flowing sodium hydroxide solution and cobalt sulfate solution obtained in step S3 into the reactor at the same time, heating and continuously stirring the reaction under alkaline conditions, and continuously injecting oxygen. After the stirring reaction is completed, filtering to obtain precipitate and mother liquor, washing and drying the precipitate to obtain cobalt hydroxide oxide, using barium hydroxide solution to remove impurities from the mother liquor until the white precipitate no longer increases, filtering to obtain reusable alkaline solution.

2. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 1, characterized in that: Step S1: disassembly and pretreatment of lithium cobalt oxide batteries, including the following steps: S1.1: Discharge and disassemble the lithium cobalt oxide battery to separate the positive electrode material, negative electrode material, separator and electrolyte; S1.2: Shelling, crushing and screening the positive electrode material to obtain positive electrode material powder; S1.3: placing the positive electrode material powder in a muffle furnace for roasting, cooling and collecting after the roasting, to obtain the positive electrode material powder; S1.4: Add the positive electrode material powder to a sodium hydroxide solution with a mass fraction of 1% according to a solid-liquid ratio (1-3):10 for alkaline leaching to remove the residual aluminum in the positive electrode material powder. After the alkaline leaching, filter to obtain the alkaline-leached positive electrode material powder.

3. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 2, characterized in that: Step S2: valuable metal leaching, specifically comprising the following steps: S2.1: Add the alkaline-leached cathode material powder into a ball mill, and then add a 0.4-1 mol / L citric acid solution and a 10-20% mass fraction hydrogen peroxide solution in sequence, and perform ball milling reaction at 50-80°C for 0.5-2h at a ball milling speed of 60-90rpm; S2.2: After the ball milling is completed, the material in the ball mill tank is poured out and filtered to obtain the leaching liquid and filter residue.

4. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 3, characterized in that: The solid-liquid mass ratio of the positive electrode material powder after alkaline leaching to the citric acid solution and the hydrogen peroxide solution is (1-2): (2-5): (2-5).

5. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 4, characterized in that: Step S3: extraction and separation, specifically comprising the following steps: S3.1: diluting di(2-ethylhexyl) phosphate with kerosene to obtain a di(2-ethylhexyl) phosphate solution with a volume concentration of 15-25%, saponifying the di(2-ethylhexyl) phosphate solution with a mass fraction of 20-40% sodium hydroxide solution, wherein the volume ratio of the di(2-ethylhexyl) phosphate solution to the sodium hydroxide solution is (1-2):1, and the saponification rate is controlled at 30-60%, thereby obtaining an organic extractant A; S3.2: using kerosene to dilute 2-ethylhexyl phosphate mono-2-ethylhexyl ester to obtain a 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution having a volume concentration of 15-25%, and saponifying the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution with a sodium hydroxide solution having a mass fraction of 20-40%, wherein the volume ratio of the 2-ethylhexyl phosphate mono-2-ethylhexyl ester solution to the sodium hydroxide solution is (1-2):1, and the saponification rate is controlled at 50-70%, thereby obtaining an organic extractant B; S3.3: adding an organic extractant A to the leachate so that the Cu, Mn, and Fe impurities in the leachate are extracted into the organic extractant A, thereby removing the Cu, Mn, and Fe impurities, while Li and Co remain in the aqueous solution; subsequently, separating and conducting the aqueous solution with Li and Co remaining, and adding an organic extractant B to the aqueous solution so that the Co in the aqueous solution is extracted into the organic extractant B, while Li continues to remain in the aqueous solution; S3.4: Separate and extract the organic extractant B that has been extracted with Co, add sulfuric acid solution to the organic extractant B that has been extracted with Co for back extraction to obtain a cobalt sulfate solution.

6. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 5, characterized in that: The volume ratio of the organic extractant A to the leaching solution is (1-3):

1.

7. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 6, characterized in that: The volume ratio of the organic extractant B to the aqueous phase solution is (1-3):

1.

8. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 7, characterized in that: Step S4: producing cobalt oxyhydroxide and recycling the mother liquor, specifically comprising the following steps: S4.1: A sodium hydroxide solution having a mass fraction of 30 to 40% and the cobalt sulfate solution obtained in step S3.3 are simultaneously flowed into the reactor, so that the pH value of the liquid in the reactor is controlled at 10.4 to 12, and the reaction is continuously stirred at 60 to 90° C., while oxygen is continuously injected until the cobalt sulfate solution no longer flows into the reactor, and the reaction is continuously stirred for 30 to 50 minutes; S4.2: After the stirring reaction is completed, the reacted material in the reactor is filtered to obtain a precipitate and a mother liquor. The precipitate is washed and dried to obtain cobalt oxyhydroxide; S4.3: Add 0.1 mol / L barium hydroxide solution dropwise to the mother liquor while stirring until the white precipitate no longer increases, and then filter the mother liquor after the reaction to remove the generated white precipitate to obtain reusable alkali solution.

9. The method for recycling waste lithium batteries to produce cobalt oxide and reusing mother liquor in the production process according to claim 8, characterized in that: The injection rate of oxygen is 10 to 60 L / min.