Method for recycling ternary black powder lithium extraction slag

Abstract

The invention provides a recycling method of ternary black powder lithium extraction slag, which comprises the following steps: mixing ternary black powder lithium extraction slag, a pH regulator, a reducing agent and a solvent under normal pressure, carrying out first-stage leaching reaction, and carrying out solid-liquid separation to obtain first-stage leachate and first-stage leaching slag; in the oxygen atmosphere, the first-stage leaching residues and acid liquor are mixed at high pressure, a second-stage leaching reaction is conducted, and second-stage leaching liquid and second-stage leaching residues are obtained after solid-liquid separation; mixing the first-stage leachate, the second-stage leachate, an oxidizing agent and a neutralizing agent, and carrying out precipitation reaction to obtain a solution with iron and aluminum removed; and sequentially carrying out impurity extraction and nickel-cobalt extraction separation on the solution subjected to iron and aluminum removal to respectively obtain a nickel salt solution and a cobalt salt solution. According to the combined process provided by the invention, the problem of low leaching rate of high-valence oxides of nickel, cobalt and manganese in the lithium extraction slag is solved, and efficient separation and purification of nickel, cobalt and manganese are realized; the process is economical, efficient and short in flow and has good application potential.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery resource recycling technology, specifically involving a method for recycling lithium extraction slag from ternary lithium black powder. Background Technology

[0002] Currently, the efficient recycling of spent lithium-ion batteries, especially ternary cathode materials rich in valuable metals such as nickel, cobalt, and manganese, has become an essential requirement for achieving sustainable resource utilization and environmental protection. In the recycling process of ternary cathode materials, lithium is typically extracted first using hydrometallurgical methods, and the resulting "lithium extraction slag" becomes the main carrier for enriching core strategic metals such as nickel, cobalt, and manganese. How to economically and efficiently recover these valuable metals from this lithium extraction slag and directly convert them into high-value-added battery-grade products is a core technological challenge in the field of resource recycling.

[0003] In lithium extraction slag, nickel, cobalt, and manganese exist primarily in the form of high-valence oxides. These compounds exhibit strong chemical stability and a dense crystal structure, making it difficult for traditional atmospheric pressure leaching processes to disrupt their structure. This results in generally low metal leaching rates, with a large amount of valuable metal remaining in the slag and causing waste. To improve leaching efficiency, existing technologies often employ chemical reducing agents such as sodium sulfite and iron powder to enhance leaching. However, these reducing agents suffer from high dosage and cost, and they easily introduce new impurities (such as iron ions), increasing the burden on subsequent purification processes and leading to lengthy and uneconomical processes.

[0004] Furthermore, existing technical solutions often focus on the initial enrichment of metals in the subsequent treatment of leachate, making it difficult to achieve efficient separation and deep purification of nickel, cobalt, and manganese. If impurities such as iron, aluminum, calcium, and magnesium, which are usually coexisting in leachate, cannot be effectively removed, they will seriously affect the purity of the final product, making it difficult for the purity of the final product to meet battery-grade standards. This limits the high-value application of lithium extraction slag recovery products.

[0005] Therefore, how to solve the problem of low leaching rate caused by the difficulty in leaching high-valence oxides of nickel, cobalt, and manganese in lithium extraction slag in an economical and efficient manner, and how to achieve efficient separation and purification of nickel, cobalt, and manganese to shorten the preparation process of battery-grade products, has become a hot research topic. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for the recycling of lithium extraction slag from ternary lithium black powder. This invention employs a combined process of "atmospheric pressure reducing acid leaching - oxygen pressure enhanced leaching - extraction for impurity removal and extraction separation," which not only solves the problem of low leaching rates caused by the difficulty in leaching high-valence oxides of nickel, cobalt, and manganese in the lithium extraction slag, but also achieves efficient separation and deep purification of nickel, cobalt, and manganese. The resulting nickel salt solution and cobalt salt solution can be directly used to prepare battery-grade products. This combined process is economical and efficient, significantly shortening the process flow from lithium extraction from ternary lithium black powder to battery-grade products, with lower energy consumption and equipment investment, and has good application potential.

[0007] To achieve this objective, the present invention adopts the following technical solution: This invention provides a method for recycling lithium extraction residue from ternary black powder, the recycling method comprising the following steps: The lithium extraction residue from ternary black powder, pH adjuster, reducing agent and solvent are mixed at normal pressure and subjected to a first-stage leaching reaction. After solid-liquid separation, a first-stage leachate and a first-stage leaching residue are obtained.

[0008] In an oxygen atmosphere, the first-stage leaching residue and acid solution are mixed under high pressure to carry out a second-stage leaching reaction. After solid-liquid separation, a second-stage leachate and a second-stage leaching residue are obtained.

[0009] The first-stage leachate, the second-stage leachate, the oxidant, and the neutralizing agent are mixed and subjected to a precipitation reaction to obtain a solution after iron and aluminum removal.

[0010] The solution after removing iron and aluminum is subjected to extraction to remove impurities and extraction to separate nickel and cobalt, respectively, to obtain nickel salt solution and cobalt salt solution.

[0011] This invention utilizes a combined process of "atmospheric pressure reducing acid leaching - oxygen pressure enhanced leaching - extraction for impurity removal and extraction separation." This process not only solves the problem of low leaching rates caused by the difficulty in leaching high-valence oxides of nickel, cobalt, and manganese in lithium extraction residue, but also achieves efficient separation and deep purification of nickel, cobalt, and manganese. The resulting nickel and cobalt salt solutions can be directly used to prepare battery-grade products. This combined process is economical and efficient, significantly shortening the process flow from lithium extraction from ternary black powder to battery-grade products, with lower energy consumption and equipment investment, and has good application potential.

[0012] In the combined process provided by this invention, the purpose of atmospheric pressure reducing acid leaching is to reduce high-valence metal oxides to easily soluble low-valence states, thereby achieving efficient preliminary leaching of valuable metals such as nickel, cobalt, and manganese. This reduces the processing load of subsequent steps and lays the foundation for subsequent deep extraction and purification. The oxygen pressure enhanced leaching process can completely destroy a portion of the stable phase remaining in the leaching residue through an oxidizing environment, achieving deep extraction of residual valuable metals and further improving the recovery rate of valuable metals. Manganese recovery is obtained by washing the extracted organic phase after impurity removal, resulting in excellent separation and a high-purity manganese-rich solution. Using the extraction separation process, efficient separation of nickel and cobalt can be achieved. The obtained pure nickel and cobalt salt solutions can be directly used in the preparation of battery-grade products, avoiding the problems of low purity, long process, and unstable yield associated with traditional lengthy chemical precipitation methods. This achieves a short closed-loop process from waste to high-end products.

[0013] It should be noted that atmospheric pressure refers to one standard atmosphere, which has a value of 101.325 kPa.

[0014] Preferably, the pH adjuster comprises concentrated sulfuric acid. It should be noted that the concentrated sulfuric acid is an aqueous solution of sulfuric acid with a mass fraction ≥ 70%, for example, the mass fraction can be 70%, 75%, 80%, 85%, 90%, or 95%, etc.

[0015] Preferably, the reducing agent comprises sodium metabisulfite.

[0016] Preferably, the mass ratio of the lithium extraction residue from the ternary black powder to the reducing agent is 1:(0.2-0.4), for example, it can be 1:0.2, 1:0.25, 1:0.3, 1:0.35 or 1:0.4, etc.

[0017] Preferably, the atmospheric pressure mixing step includes: The lithium extraction residue from ternary black powder is mixed with solvent and slurryed, and then a pH adjuster and a reducing agent are added to obtain a mixed solution.

[0018] Preferably, the pH of the mixed solution is 0.5-1.5, for example, it can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4 or 1.5.

[0019] Preferably, the temperature of the leaching reaction is 70-80°C, for example, 70°C, 75°C or 80°C.

[0020] Preferably, the leaching reaction time is 1-2 hours, for example, 1 hour, 1.5 hours or 2 hours.

[0021] Preferably, the acid solution includes sulfuric acid.

[0022] In the oxygen pressure enhanced leaching stage of this invention, sulfuric acid is introduced to provide a strongly acidic reaction environment. Under the synergistic effect of high pressure and oxygen, stable compounds (such as oxides and complex salts) of metals such as nickel and cobalt that have not been completely destroyed in a section of the leaching residue are thoroughly acid-leached out, and the low pH value of the solution is maintained to prevent premature hydrolysis and precipitation of metal ions.

[0023] Preferably, the sulfuric acid is concentrated sulfuric acid, and the mass fraction of the concentrated sulfuric acid is 80-90%, for example, it can be 80%, 85% or 90%, etc.

[0024] Preferably, the mass-to-volume ratio of the leaching residue to the acid solution is 100g:(30-40)mL, for example, it can be 100g:30mL, 100g:35mL or 100g:40mL, etc.

[0025] In this invention, the appropriate amount of acid solution for a single leaching residue can ensure thorough leaching reaction and improve metal recovery rate while avoiding increased costs and aggravated equipment corrosion, thus achieving a balance between economic benefits and leaching efficiency.

[0026] Preferably, during the high-pressure mixing process, the ambient pressure is 0.3-0.5 MPa, for example, 0.3 MPa, 0.4 MPa, or 0.5 MPa. Appropriate pressure enhances the dissolution and mass transfer of oxygen in the solution, providing sufficient oxygen partial pressure for the oxidation reaction, thereby effectively oxidizing and decomposing the insoluble phases in the slag, and significantly improving the leaching rate and overall recovery rate of valuable metals.

[0027] Preferably, the temperature of the two-stage leaching reaction is 140-150°C, for example, 140°C, 145°C, or 150°C.

[0028] Preferably, the two-stage leaching reaction takes 6-8 hours, for example, 6 hours, 7 hours, or 8 hours.

[0029] Preferably, the step of mixing the first-stage leachate, the second-stage leachate, the oxidant, and the neutralizing agent includes: The first and second leachates are mixed to obtain a mixed leachate; then the mixed leachate is mixed with an oxidant, and finally a neutralizing agent is added.

[0030] Preferably, the oxidant includes hydrogen peroxide.

[0031] Preferably, the ratio of the molar amount of iron to the molar amount of the oxidant in the mixed leachate is 1:(1.2-1.8), for example, it can be 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7 or 1:1.8, etc.

[0032] The present invention introduces an oxidant at the above ratio to ensure that ferrous ions in the leachate are completely oxidized to ferric ions, thereby fully removing iron. This ratio takes into account the utilization rate of the oxidant in the actual reaction and the consumption of possible side reactions, and can effectively overcome the interference of other reducing substances in the solution, ensuring that the oxidation of iron ions is thorough and without residue, thereby completely removing iron and aluminum, laying the foundation for the deep purification of nickel and cobalt solutions.

[0033] Preferably, the neutralizing agent comprises any one or a combination of at least two of sodium hydroxide, sodium carbonate, or calcium oxide.

[0034] Preferably, the temperature of the precipitation reaction is 65-75°C, for example, 65°C, 70°C or 75°C.

[0035] Preferably, the precipitation reaction time is 45-60 min, for example, 45 min, 50 min, 55 min or 60 min.

[0036] Preferably, the extraction and impurity removal step includes: The solution after iron and aluminum removal is subjected to a first countercurrent extraction using a first extractant to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities deeply removed.

[0037] Preferably, the first extractant comprises P204 extractant.

[0038] Preferably, the saponification rate of the P204 extractant is 70-80%, for example, it can be 70%, 75%, or 80%. It should be noted that "saponification rate" refers to the percentage (in mole fraction) of the number of P204 molecules undergoing saponification reaction during the saponification treatment. The same applies below.

[0039] Preferably, the conditions for the first countercurrent extraction include: After removing iron and aluminum, the pH of the solution is 3-3.5, and the volume ratio of the organic phase to the aqueous phase is 1:(4-5), for example, it can be 1:4, 1:4.2, 1:4.4, 1:4.6, 1:4.8 or 1:5, etc.

[0040] This invention utilizes countercurrent extraction under the aforementioned conditions, which facilitates the efficient and selective separation of heavy metal impurities from nickel and cobalt. Controlling the pH within a weakly acidic range of 3-3.5 allows heavy metal impurities to be preferentially and fully extracted into the organic phase, while minimizing co-extraction losses of nickel and cobalt. The 1:(4-5) ratio (O / A) means that during countercurrent extraction, a relatively large amount of aqueous phase and a limited amount of organic phase are in full contact. This not only improves the mass transfer driving force and extraction thoroughness of impurities, ensuring the purity of the raffinate (aqueous phase), but also significantly reduces the amount of organic phase used and the subsequent processing load, making the entire impurity removal process both deeply purified and economical.

[0041] Preferably, the extract containing heavy metal impurities is washed to selectively separate manganese, resulting in a manganese-rich washing solution.

[0042] The present invention uses the above-mentioned method to recover manganese, which not only purifies the organic phase, but more importantly, achieves efficient separation of manganese from other stubborn impurities (such as copper and zinc), thereby recovering manganese as a by-product.

[0043] Preferably, the washing process includes: mixing the extract containing heavy metal impurities and the washing solution for washing.

[0044] Preferably, the washing solution is dilute sulfuric acid with a concentration of 0.1-0.25 mol / L, such as 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or 0.25 mol / L.

[0045] Preferably, the step of extracting and separating nickel and cobalt includes: The raffinate is subjected to a second countercurrent extraction using a second extractant to obtain a cobalt-loaded organic phase and a nickel salt solution. The cobalt-loaded organic phase is then back-extracted to obtain a cobalt salt solution.

[0046] Preferably, the second extractant comprises P507 extractant.

[0047] Preferably, the saponification rate of the P507 extractant is 80-85%, for example, it can be 80%, 81%, 82%, 83%, 84% or 85%, etc.

[0048] Preferably, the conditions for the second countercurrent extraction include: After removing iron and aluminum, the pH of the solution is 5-5.5, for example, it can be 5, 5.1, 5.2, 5.3, 5.4 or 5.5, etc., and the volume ratio of organic phase to aqueous phase is 1:(1.2-1.5), for example, it can be 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc.

[0049] This invention utilizes countercurrent extraction under the aforementioned conditions, which facilitates highly selective and efficient separation of nickel and cobalt. Specifically, controlling the pH within the range of 5-5.5 is based on the significant difference in the extraction equilibrium of cobalt and nickel by the second extractant (such as P507). Within this pH window, cobalt is preferentially extracted into the organic phase, while nickel is retained to the maximum extent in the aqueous phase, thus achieving efficient separation of the two. Using a 1:(1.2-1.5) ratio (O / A) provides the optimal balance between mass transfer driving force and processing capacity for the multi-stage countercurrent extraction process. This ensures sufficient cobalt loading in the organic phase for high cobalt yield while maintaining extremely low cobalt residue in the aqueous phase (nickel salt solution), resulting in a high-purity nickel salt solution.

[0050] Preferably, the recycling method includes the following steps: (1) The lithium extraction residue from ternary black powder and water are mixed and slurried at a liquid-solid ratio of (5-10):1 (for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.). Then, a pH adjuster is added to adjust the pH of the slurry to 0.5-1.5, and a reducing agent is added to obtain a mixed solution. Then, a first-stage leaching reaction is carried out at 70-80℃, normal pressure and stirring for 1-2 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a first-stage leachate and a first-stage leaching residue. The pH adjuster includes concentrated sulfuric acid; the reducing agent includes sodium metabisulfite; the mass ratio of the lithium extraction residue from ternary black powder to the reducing agent is 1:(0.2-0.4).

[0051] (2) The first-stage leaching residue and sulfuric acid are mixed at a mass-volume ratio of 100g:(30-40)mL and transferred to a high-pressure reactor. Oxygen is introduced and a second-stage leaching reaction is carried out at 140-150℃ under an oxygen atmosphere for 6-8 hours. After the reaction is completed, solid-liquid separation is performed to obtain a second-stage leaching solution and a second-stage leaching residue. The pressure of the high-pressure reactor is 0.3-0.5MPa.

[0052] (3) The first-stage leachate and the second-stage leachate are mixed to obtain a mixed leachate. Then, an oxidant is added to the mixed leachate, and the temperature is controlled at 65-75℃. Then, a neutralizing agent is slowly added to adjust the pH to 3.8-4.2. A precipitation reaction is carried out for 45-60 minutes to allow iron and aluminum to hydrolyze and precipitate. The solution is filtered to obtain a solution after removing iron and aluminum. The ratio of the molar amount of iron to the molar amount of the oxidant in the mixed leachate is 1:(1.2-1.8). The neutralizing agent includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, or calcium oxide.

[0053] (4) The solution after iron and aluminum removal is subjected to a first countercurrent extraction of 4-5 stages (e.g., 4 or 5 stages) using P204 extractant with a saponification rate of 70-80% to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities deeply removed; wherein, the conditions for the first countercurrent extraction include: the pH of the solution after iron and aluminum removal is 3-3.5, and the volume ratio of organic phase to aqueous phase is 1:(4-5); the extract containing heavy metal impurities includes copper ions, zinc ions, manganese ions, calcium ions and magnesium ions.

[0054] (5) The raffinate is subjected to a second countercurrent extraction of 6-7 stages (e.g., 6 or 7 stages) using P507 extractant with a saponification rate of 80-85% to obtain a cobalt-loaded organic phase and a nickel sulfate solution; wherein the conditions for the second countercurrent extraction include: the pH of the solution after removing iron and aluminum is 5-5.5, and the volume ratio of the organic phase to the aqueous phase is 1:(1.2-1.5).

[0055] The cobalt-loaded organic phase is back-extracted using dilute sulfuric acid to obtain a cobalt sulfate solution; wherein the concentration of the dilute sulfuric acid is 1.5-2.5 mol / L (for example, it can be 1.5 mol / L, 2 mol / L or 3 mol / L).

[0056] (6) Concentrate the nickel sulfate solution and cobalt sulfate solution to a specific gravity of 1.55-1.65 g / cm³, respectively. 3 (For example, it could be 1.55 g / cm³) 3 1.6g / cm 3 Or 1.65g / cm 3 Then, cool and crystallize at a rate of 5-10℃ / h (e.g., 5℃ / h, 6℃ / h, 7℃ / h, 8℃ / h, 9℃ / h or 10℃ / h, etc.), and dry to obtain battery-grade nickel sulfate and battery-grade cobalt sulfate, respectively.

[0057] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0058] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a combined process of "atmospheric pressure reducing acid leaching - oxygen pressure enhanced leaching - extraction for impurity removal and extraction separation." This process not only solves the problem of low leaching rates caused by the difficulty in leaching high-valence oxides of nickel, cobalt, and manganese in lithium extraction slag, but also achieves efficient separation and deep purification of nickel, cobalt, and manganese. The resulting nickel and cobalt salt solutions can be directly used to prepare battery-grade products. This combined process is economical and efficient, significantly shortening the process flow from lithium extraction from ternary black powder to battery-grade products, with lower energy consumption and equipment investment, and has good application potential. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0060] It should be noted that the main components of the lithium extraction slag from ternary black powder in the following embodiments are shown in Table 1 below: Table 1 Example 1 This embodiment provides a method for recycling lithium extraction residue from ternary black powder, the recycling method including the following steps: (1) The lithium extraction residue from ternary black powder and water are mixed and slurried at a liquid-solid ratio of 10:1. Then, concentrated sulfuric acid is added to adjust the pH of the slurry to 1, and sodium metabisulfite is added to obtain a mixed solution. Then, a first-stage leaching reaction is carried out at 70°C, normal pressure and stirring for 2 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a first-stage leaching solution and a first-stage leaching residue. The mass ratio of the lithium extraction residue from ternary black powder to the sodium metabisulfite is 1:0.4.

[0061] (2) The first-stage leaching residue and concentrated sulfuric acid with a mass fraction of 85% are mixed at a mass-volume ratio of 100g:40mL and transferred to a high-pressure reactor. Oxygen is introduced and a second-stage leaching reaction is carried out at 150°C under an oxygen atmosphere for 8 hours. After the reaction is completed, solid-liquid separation is performed to obtain the second-stage leaching solution and the second-stage leaching residue. The pressure of the high-pressure reactor is 0.4MPa.

[0062] (3) The first-stage leachate and the second-stage leachate are mixed to obtain a mixed leachate. Then, hydrogen peroxide is added to the mixed leachate, the temperature is controlled at 70°C, and then a neutralizing agent is slowly added to adjust the pH to 4.2. A precipitation reaction is carried out for 60 minutes to allow iron and aluminum to hydrolyze and precipitate. The solution is filtered to obtain a solution after removing iron and aluminum. The ratio of the molar amount of iron to the molar amount of hydrogen peroxide in the mixed leachate is 1:1.5. The neutralizing agent is sodium hydroxide.

[0063] (4) The solution after iron and aluminum removal is subjected to a first countercurrent extraction in 5 stages using P204 extractant with a saponification rate of 75% to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities deeply removed; wherein, the conditions for the first countercurrent extraction include: the pH of the solution after iron and aluminum removal is 3.5, and the volume ratio of organic phase to aqueous phase is 1:4.5; the extract containing heavy metal impurities includes copper ions, zinc ions, manganese ions, calcium ions and magnesium ions.

[0064] The extract containing heavy metal impurities was mixed with 0.2 mol / L dilute sulfuric acid and washed to obtain a manganese-rich washing solution.

[0065] (5) The raffinate was subjected to a second countercurrent extraction in 7 stages using P507 extractant with a saponification rate of 85% to obtain an organic phase loaded with cobalt and a nickel sulfate solution; wherein the conditions for the second countercurrent extraction included: the pH of the solution after removing iron and aluminum was 5.5, and the volume ratio of the organic phase to the aqueous phase was 1:1.3.

[0066] The cobalt-loaded organic phase was back-extracted using dilute sulfuric acid to obtain a cobalt sulfate solution; wherein the concentration of the dilute sulfuric acid was 2 mol / L.

[0067] (6) The nickel sulfate solution and cobalt sulfate solution are concentrated to a specific gravity of 1.6 g / cm³. 3 Then, the mixture was cooled and crystallized at a rate of 5℃ / h, and dried to obtain battery-grade nickel sulfate and battery-grade cobalt sulfate, respectively.

[0068] Example 2 This embodiment provides a method for recycling lithium extraction residue from ternary black powder, the recycling method including the following steps: (1) The lithium extraction residue from ternary black powder and water are mixed and slurried at a liquid-solid ratio of 5:1. Then, concentrated sulfuric acid is added to adjust the pH of the slurry to 1.5, and sodium metabisulfite is added to obtain a mixed solution. Then, a first-stage leaching reaction is carried out at 75°C, normal pressure and stirring for 1.5 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a first-stage leaching solution and a first-stage leaching residue. The mass ratio of the lithium extraction residue from ternary black powder to the sodium metabisulfite is 1:0.2.

[0069] (2) The first-stage leaching residue and concentrated sulfuric acid with a mass fraction of 85% are mixed at a mass-volume ratio of 100g:30mL and transferred to a high-pressure reactor. Oxygen is introduced and a second-stage leaching reaction is carried out at 140℃ under an oxygen atmosphere for 7 hours. After the reaction is completed, solid-liquid separation is performed to obtain the second-stage leaching solution and the second-stage leaching residue. The pressure of the high-pressure reactor is 0.3MPa.

[0070] (3) The first-stage leachate and the second-stage leachate are mixed to obtain a mixed leachate. Then hydrogen peroxide is added to the mixed leachate, the temperature is controlled at 65°C, and then a neutralizing agent is slowly added to adjust the pH to 4. A precipitation reaction is carried out for 50 minutes to allow iron and aluminum to hydrolyze and precipitate. The solution is filtered to obtain a solution after removing iron and aluminum. The ratio of the molar amount of iron to the molar amount of hydrogen peroxide in the mixed leachate is 1:1.2. The neutralizing agent is sodium hydroxide.

[0071] (4) The solution after iron and aluminum removal is subjected to a first countercurrent extraction in 5 stages using P204 extractant with a saponification rate of 70% to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities deeply removed; wherein, the conditions for the first countercurrent extraction include: the pH of the solution after iron and aluminum removal is 3, and the volume ratio of organic phase to aqueous phase is 1:4; the extract containing heavy metal impurities includes copper ions, zinc ions, manganese ions, calcium ions and magnesium ions.

[0072] The extract containing heavy metal impurities was mixed with 0.2 mol / L dilute sulfuric acid and washed to obtain a manganese-rich washing solution.

[0073] (5) The raffinate was subjected to a second countercurrent extraction in 7 stages using P507 extractant with a saponification rate of 80% to obtain an organic phase loaded with cobalt and a nickel sulfate solution; wherein the conditions for the second countercurrent extraction included: the pH of the solution after removing iron and aluminum was 5, and the volume ratio of the organic phase to the aqueous phase was 1:1.2.

[0074] The organic phase loaded with cobalt was back-extracted using dilute sulfuric acid to obtain a cobalt sulfate solution; wherein the concentration of the dilute sulfuric acid was 1.5 mol / L.

[0075] (6) The nickel sulfate solution and cobalt sulfate solution are concentrated to a specific gravity of 1.55 g / cm³. 3 Then, the mixture was cooled and crystallized at a rate of 8℃ / h, and dried to obtain battery-grade nickel sulfate and battery-grade cobalt sulfate, respectively.

[0076] Example 3 This embodiment provides a method for recycling lithium extraction residue from ternary black powder, the recycling method including the following steps: (1) The lithium extraction residue from ternary black powder and water are mixed and slurried at a liquid-solid ratio of 8:1. Then, concentrated sulfuric acid is added to adjust the pH of the slurry to 1, and sodium metabisulfite is added to obtain a mixed solution. Then, a first-stage leaching reaction is carried out at 80°C, normal pressure and stirring for 1 hour. After the reaction is completed, solid-liquid separation is carried out to obtain a first-stage leaching solution and a first-stage leaching residue. The mass ratio of the lithium extraction residue from ternary black powder to the sodium metabisulfite is 1:0.3.

[0077] (2) The first-stage leaching residue and concentrated sulfuric acid with a mass fraction of 85% are mixed at a mass-volume ratio of 100g:35mL and transferred to a high-pressure reactor. Oxygen is introduced and a second-stage leaching reaction is carried out at 145℃ under an oxygen atmosphere for 6 hours. After the reaction is completed, solid-liquid separation is performed to obtain the second-stage leaching solution and the second-stage leaching residue. The pressure of the high-pressure reactor is 0.5MPa.

[0078] (3) The first-stage leachate and the second-stage leachate are mixed to obtain a mixed leachate. Then hydrogen peroxide is added to the mixed leachate, the temperature is controlled at 75°C, and then a neutralizing agent is slowly added to adjust the pH to 3.8. A precipitation reaction is carried out for 45 minutes to allow iron and aluminum to hydrolyze and precipitate. The solution is filtered to obtain a solution after removing iron and aluminum. The ratio of the molar amount of iron to the molar amount of hydrogen peroxide in the mixed leachate is 1:1.8. The neutralizing agent is sodium hydroxide.

[0079] (4) The solution after iron and aluminum removal is subjected to a first countercurrent extraction in 5 stages using P204 extractant with a saponification rate of 80% to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities removed to a greater extent; wherein, the conditions for the first countercurrent extraction include: the pH of the solution after iron and aluminum removal is 3.2, and the volume ratio of organic phase to aqueous phase is 1:5; the extract containing heavy metal impurities includes copper ions, zinc ions, manganese ions, calcium ions and magnesium ions.

[0080] The extract containing heavy metal impurities was mixed with 0.2 mol / L dilute sulfuric acid and washed to obtain a manganese-rich washing solution.

[0081] (5) The raffinate was subjected to a second countercurrent extraction in 7 stages using P507 extractant with a saponification rate of 82% to obtain an organic phase loaded with cobalt and a nickel sulfate solution; wherein the conditions for the second countercurrent extraction included: the pH of the solution after removing iron and aluminum was 5.2, and the volume ratio of the organic phase to the aqueous phase was 1:1.5.

[0082] The organic phase loaded with cobalt was back-extracted using dilute sulfuric acid to obtain a cobalt sulfate solution; wherein the concentration of the dilute sulfuric acid was 2.5 mol / L.

[0083] (6) The nickel sulfate solution and cobalt sulfate solution are concentrated to a specific gravity of 1.65 g / cm³. 3 Then, the mixture was cooled and crystallized at a rate of 10℃ / h, and dried to obtain battery-grade nickel sulfate and battery-grade cobalt sulfate, respectively.

[0084] Example 4 The difference between this embodiment and embodiment 1 is that the temperature of the first leaching reaction in step (1) is 75°C, and the temperature of the second leaching reaction in step (2) is 140°C.

[0085] The remaining recycling methods and parameters are consistent with those in Example 1.

[0086] Example 5 The difference between this embodiment and embodiment 1 is that the time for the first leaching reaction in step (1) is 1.5 hours, and the time for the second leaching reaction in step (2) is 6 hours.

[0087] The remaining recycling methods and parameters are consistent with those in Example 1.

[0088] Example 6 The difference between this embodiment and Embodiment 1 is as follows: (1) The lithium extraction residue from ternary black powder and water are mixed and slurried at a liquid-solid ratio of 8:1. Then, concentrated sulfuric acid is added to adjust the pH of the slurry to 1, and sodium metabisulfite is added to obtain a mixed solution. Then, a first-stage leaching reaction is carried out at 72°C, normal pressure and stirring for 2 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a first-stage leaching solution and a first-stage leaching residue. The mass ratio of the lithium extraction residue from ternary black powder to the sodium metabisulfite is 1:0.35.

[0089] (2) The first-stage leaching residue and concentrated sulfuric acid with a mass fraction of 85% are mixed at a mass-volume ratio of 100g:35mL and transferred to a high-pressure reactor. Oxygen is introduced and the second-stage leaching reaction is carried out at 150℃ under an oxygen atmosphere for 8 hours. After the reaction is completed, solid-liquid separation is carried out to obtain the second-stage leaching solution and the second-stage leaching residue.

[0090] The remaining recycling methods and parameters are consistent with those in Example 1.

[0091] Example 7 The difference between this embodiment and embodiment 1 is that in step (1), concentrated sulfuric acid is added to adjust the pH of the slurry to 0.31.

[0092] The remaining recycling methods and parameters are consistent with those in Example 1.

[0093] Example 8 The difference between this embodiment and embodiment 1 is that in step (1), the liquid-solid ratio of the lithium extraction residue from ternary black powder to water is 5:1, and the mass ratio of the lithium extraction residue from ternary black powder to sodium metabisulfite is 1:0.15; in step (2), the mass-volume ratio of the first-stage leaching residue to concentrated sulfuric acid is 100g:30mL.

[0094] The remaining recycling methods and parameters are consistent with those in Example 1.

[0095] Example 9 The difference between this embodiment and embodiment 1 is that, in step (5), the pH of the solution after removing iron and aluminum is 4 in the second countercurrent extraction conditions.

[0096] The remaining recycling methods and parameters are consistent with those in Example 1.

[0097] Comparative Example 1 The difference between this comparative example and Example 1 is that in step (1), the liquid-solid ratio of the lithium extraction residue from ternary black powder to water is 5:1, and the mass ratio of the lithium extraction residue from ternary black powder to sodium metabisulfite is 1:0.1; in step (2), oxygen is replaced by sodium thiosulfate, and the mass-volume ratio of the first-stage leaching residue to concentrated sulfuric acid is 100g:35mL.

[0098] The remaining recycling methods and parameters are consistent with those in Example 1.

[0099] Comparative Example 2 The difference between this comparative example and Example 1 is that sodium metabisulfite is not added in step (1).

[0100] The remaining recycling methods and parameters are consistent with those in Example 1.

[0101] Comparative Example 3 The difference between this comparative example and Example 1 is that the high-pressure reactor in step (2) is replaced with an atmospheric pressure reactor.

[0102] The remaining recycling methods and parameters are consistent with those in Example 1.

[0103] Comparative Example 4 The difference between this comparative example and Example 1 is that step (4) is omitted.

[0104] The remaining recycling methods and parameters are consistent with those in Example 1.

[0105] Performance testing Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to test the total leaching rates of cobalt, nickel, and manganese in the mixed leaching solutions provided in the above examples and comparative examples. The formulas for calculating the total leaching rate of cobalt are: (total mass of cobalt in the mixed leaching solution / total mass of cobalt in the raw material) × 100%, the formulas for calculating the total leaching rate of nickel are: (total mass of nickel in the mixed leaching solution / total mass of nickel in the raw material) × 100%, and the formulas for calculating the total leaching rate of manganese are: (total mass of manganese in the mixed leaching solution / total mass of manganese in the raw material) × 100%.

[0106] The residual iron and aluminum in the solutions provided by the above examples and comparative examples after iron and aluminum removal were tested using the ICP-OES method.

[0107] The raffinate with deep removal of heavy metal impurities provided in the above examples and comparative examples was tested using the ICP-OES method to obtain the residual manganese, zinc and calcium content.

[0108] The cobalt content in the nickel sulfate solutions provided in the above examples and comparative examples, as well as the nickel content in the cobalt sulfate solutions, were tested using the ICP-OES method.

[0109] The test results are shown in Table 2.

[0110] Table 2 analyze: As shown in Table 2, this invention, through a combined process of "atmospheric pressure reducing acid leaching - oxygen pressure enhanced leaching - extraction for impurity removal and extraction separation," not only solves the problem of low leaching rates caused by the difficulty in leaching high-valence oxides of nickel, cobalt, and manganese in lithium extraction slag, but also achieves efficient separation and deep purification of nickel, cobalt, and manganese. The resulting nickel salt solution and cobalt salt solution can be directly used to prepare battery-grade products. This combined process is economical and efficient, significantly shortening the process flow from lithium extraction from ternary black powder to battery-grade products, with lower energy consumption and equipment investment, and has good application potential.

[0111] As can be seen from the comparison between Example 1 and Example 7, if the pH of the slurry is too low after adjustment, the acidity will be too strong, which may affect the subsequent hydrolysis and extraction balance, resulting in a slight decrease in the metal leaching rate, incomplete removal of impurities, and significantly affecting the separation selectivity of P507 for nickel and cobalt.

[0112] A comparison between Example 1 and Example 8 shows that when the amount of reducing agent is too small, the leaching and purification efficiency decreases.

[0113] As can be seen from the comparison between Example 1 and Example 9, if the pH of the solution after removing iron and aluminum is too low in the second countercurrent extraction conditions in step (5), the cobalt extraction rate is extremely low and cobalt and nickel cannot be separated.

[0114] As can be seen from the comparison between Example 1 and Comparative Example 1, if the amount of reducing agent is too small and oxygen is replaced with sodium thiosulfate at the same time, the second-stage leaching effect is poor, resulting in a decrease in the leaching rate of nickel and cobalt, an increase in the leaching of impurities, a heavy burden on subsequent purification, and low purity of the final product.

[0115] As can be seen from the comparison between Example 1 and Comparative Example 2, if sodium metabisulfite is not added in step (1), the high-valence metals are not reduced, the leaching rate of one stage is extremely low, and the leaching rate of nickel, cobalt and manganese is low.

[0116] As can be seen from the comparison between Example 1 and Comparative Example 3, if the high-pressure reactor in step (2) is replaced by an atmospheric pressure reactor, the oxygen pressure enhancement effect is lacking, the reaction is incomplete, and the total leaching rate of nickel, cobalt and manganese is low.

[0117] As can be seen from the comparison between Example 1 and Comparative Example 4, if step (4) is not performed, although the leaching rate of nickel, cobalt and manganese remains unchanged, the impurity content is high, which will contaminate the P507 extractant, resulting in poor nickel-cobalt separation effect and serious excess of impurities such as Zn and Mn in the final product.

[0118] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling lithium extraction slag from ternary black powder, characterized in that, The recycling method includes the following steps: The lithium extraction residue from ternary black powder, pH adjuster, reducing agent and solvent are mixed at normal pressure and subjected to a first-stage leaching reaction. After solid-liquid separation, a first-stage leachate and a first-stage leaching residue are obtained. In an oxygen atmosphere, the first-stage leaching residue and acid solution are mixed under high pressure to carry out a second-stage leaching reaction. After solid-liquid separation, a second-stage leaching solution and a second-stage leaching residue are obtained. The first-stage leachate, the second-stage leachate, the oxidant, and the neutralizing agent are mixed and subjected to a precipitation reaction to obtain a solution after iron and aluminum removal. The solution after removing iron and aluminum is subjected to extraction to remove impurities and extraction to separate nickel and cobalt, respectively, to obtain nickel salt solution and cobalt salt solution.

2. The recycling method according to claim 1, characterized in that, The pH adjuster includes concentrated sulfuric acid; Preferably, the reducing agent comprises sodium metabisulfite; Preferably, the mass ratio of the lithium extraction residue from the ternary black powder to the reducing agent is 1:(0.2-0.4).

3. The recycling method according to claim 1 or 2, characterized in that, The atmospheric pressure mixing step includes: The lithium extraction residue from ternary black powder is mixed with solvent and slurryed, and then a pH adjuster and a reducing agent are added to obtain a mixed solution; Preferably, the pH of the mixed solution is 0.5-1.

5.

4. The recycling method according to any one of claims 1-3, characterized in that, The temperature of the leaching reaction is 70-80℃; Preferably, the leaching reaction time is 1-2 hours.

5. The recycling method according to any one of claims 1-4, characterized in that, The acid solution includes sulfuric acid; Preferably, the mass-to-volume ratio of the leaching residue to the acid solution is 100g:(30-40)mL; Preferably, during the high-pressure mixing process, the ambient pressure is 0.3-0.5 MPa.

6. The recycling method according to any one of claims 1-5, characterized in that, The temperature of the two-stage leaching reaction is 140-150℃; Preferably, the two-stage leaching reaction takes 6-8 hours.

7. The recycling method according to any one of claims 1-6, characterized in that, The step of mixing the first-stage leachate, the second-stage leachate, the oxidant, and the neutralizing agent includes: The first-stage leachate and the second-stage leachate are mixed to obtain a mixed leachate; then the mixed leachate is mixed with an oxidant, and finally a neutralizing agent is added; Preferably, the oxidant includes hydrogen peroxide; Preferably, the ratio of the molar amount of iron to the molar amount of the oxidant in the mixed leachate is 1:(1.2-1.8); Preferably, the neutralizing agent comprises any one or a combination of at least two of sodium hydroxide, sodium carbonate, or calcium oxide; Preferably, the precipitation reaction is carried out at a temperature of 65-75°C; Preferably, the precipitation reaction takes 45-60 minutes.

8. The recycling method according to any one of claims 1-7, characterized in that, The extraction and impurity removal steps include: The solution after iron and aluminum removal is subjected to a first countercurrent extraction using a first extractant to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities deeply removed. Preferably, the first extractant comprises P204 extractant; Preferably, the saponification rate of the P204 extractant is 70-80%; Preferably, the conditions for the first countercurrent extraction include: the pH of the solution after iron and aluminum removal is 3-3.5, and the volume ratio of the organic phase to the aqueous phase is 1:(4-5); Preferably, the extract containing heavy metal impurities is washed to selectively separate manganese, resulting in a manganese-rich washing solution.

9. The recycling method according to claim 8, characterized in that, The extraction and separation steps for nickel and cobalt include: The raffinate is subjected to a second countercurrent extraction using a second extractant to obtain a cobalt-loaded organic phase and a nickel salt solution; the cobalt-loaded organic phase is then back-extracted to obtain a cobalt salt solution. Preferably, the second extractant comprises P507 extractant; Preferably, the saponification rate of the P507 extractant is 80-85%; Preferably, the conditions for the second countercurrent extraction include: the pH of the solution after iron and aluminum removal is 5-5.5, and the volume ratio of the organic phase to the aqueous phase is 1:(1.2-1.5).

10. The recycling method according to any one of claims 1-9, characterized in that, The recycling method includes the following steps: (1) The lithium extraction residue from ternary black powder and water are mixed and slurried at a liquid-solid ratio of (5-10):

1. Then, a pH adjuster is added to adjust the pH of the slurry to 0.5-1.5, and a reducing agent is added to obtain a mixed solution. Then, a first-stage leaching reaction is carried out at 70-80℃, normal pressure and stirring for 1-2 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a first-stage leachate and a first-stage leaching residue. The pH adjuster includes concentrated sulfuric acid; the reducing agent includes sodium metabisulfite; the mass ratio of the lithium extraction residue from ternary black powder to the reducing agent is 1:(0.2-0.4). (2) The first-stage leaching residue and sulfuric acid are mixed at a mass-volume ratio of 100g:(30-40)mL and transferred to a high-pressure reactor. Oxygen is introduced, and a second-stage leaching reaction is carried out at 140-150℃ under an oxygen atmosphere for 6-8 hours. After the reaction is completed, solid-liquid separation is performed to obtain a second-stage leaching solution and a second-stage leaching residue. The pressure of the high-pressure reactor is 0.3-0.5MPa. (3) The first-stage leachate and the second-stage leachate are mixed to obtain a mixed leachate. Then, an oxidant is added to the mixed leachate, and the temperature is controlled at 65-75℃. Then, a neutralizing agent is slowly added to adjust the pH to 3.8-4.

2. A precipitation reaction is carried out for 45-60 minutes to allow iron and aluminum to hydrolyze and precipitate. The mixture is filtered to obtain a solution after removing iron and aluminum. The ratio of the molar amount of iron to the molar amount of the oxidant in the mixed leachate is 1:(1.2-1.8). The neutralizing agent includes any one or a combination of at least two of sodium hydroxide, sodium carbonate, or calcium oxide. (4) The solution after iron and aluminum removal is subjected to a first countercurrent extraction of 4-5 stages using P204 extractant with a saponification rate of 70-80% to obtain an extract containing heavy metal impurities and a raffinate with heavy metal impurities deeply removed; wherein, the conditions for the first countercurrent extraction include: the pH of the solution after iron and aluminum removal is 3-3.5, and the volume ratio of organic phase to aqueous phase is 1:(4-5); the extract containing heavy metal impurities includes copper ions, zinc ions, manganese ions, calcium ions and magnesium ions; (5) The raffinate is subjected to a second countercurrent extraction of 6-7 stages using P507 extractant with a saponification rate of 80-85% to obtain a cobalt-loaded organic phase and a nickel sulfate solution; wherein the conditions for the second countercurrent extraction include: the pH of the solution after removing iron and aluminum is 5-5.5, and the volume ratio of the organic phase to the aqueous phase is 1:(1.2-1.5). The cobalt-loaded organic phase was back-extracted using dilute sulfuric acid to obtain a cobalt sulfate solution; wherein the concentration of the dilute sulfuric acid was 1.5-2.5 mol / L. (6) The nickel sulfate solution and cobalt sulfate solution are concentrated to a specific gravity of 1.55-1.65 g / cm³, respectively. 3 Then, the mixture is cooled and crystallized at a rate of 5-10℃ / h, and dried to obtain battery-grade nickel sulfate and battery-grade cobalt sulfate, respectively.

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