A method and system for recovering valuable metals from lithium ion batteries

Abstract

The present application relates to the technical field of lithium battery recycling, in particular to a method and system for recycling valuable metals in lithium ion batteries. The method and system for recycling valuable metals in lithium ion batteries provided by the present application in-situ couples biological leaching method with membrane separation technology, and realizes simultaneous leaching and separation by introducing a membrane separation unit in the biological leaching process. In the leaching process, the immediate migration and removal of target metal ions by membrane separation technology reduces the cumulative concentration of metal ions in the biological leaching solution, breaks the chemical equilibrium in the traditional biological leaching system, promotes the leaching reaction to continuously proceed in the positive direction, significantly improves the leaching rate of metal ions, shortens the leaching period, and greatly shortens the leaching time to 1 / 2 of the original, which is conducive to realizing continuous operation of the entire recycling process.

Description

Technical Field

[0001] This invention relates to the field of lithium battery recycling technology, and specifically to a method and system for recycling valuable metals from lithium-ion batteries. Background Technology

[0002] With the rapid development of the new energy and energy storage industries, lithium-ion batteries have become the core energy carrier for electric vehicles and large-scale energy storage systems. A large number of power lithium-ion batteries will be decommissioned after reaching the end of their service life, forming a massive amount of waste battery resources. The cathode materials of waste lithium-ion batteries are rich in valuable metals such as lithium and cobalt, with metal grades significantly higher than those of natural ores, possessing significant resource recycling value. However, improper recycling and processing can easily lead to environmental pollution and safety hazards due to heavy metals and electrolyte components in waste batteries. Therefore, developing efficient, low-energy-consumption, and environmentally friendly waste lithium-ion battery metal recycling technologies is of great significance for ensuring the security of key metal resources and promoting green and low-carbon development.

[0003] Bioleaching technology utilizes microorganisms and their metabolites to dissolve metal elements in cathode materials under ambient temperature and pressure conditions, and is considered a promising green metallurgical alternative. This technology can significantly reduce chemical reagent consumption and wastewater discharge, lower energy consumption and carbon emissions, and has good adaptability to low-grade or complex battery cathode materials. Do et al. (ACS Sustainable Chem. Eng. 10 (2022) 2634-2644) used *Thiobacillus ferrooxidans* to leach valuable metals from ternary lithium batteries. Their study found that in just 6 hours, they could successfully leach 85.5% of nickel (Ni), 91.8% of manganese (Mn), 90.4% of cobalt (Co), and 89.9% of lithium (Li) from the cathode material. Yang et al. systematically investigated the effects of particle size and microbial adaptability on metal leaching behavior. The results showed that high metal recovery efficiency could be achieved under medium particle size (0.5-6 mm) conditions, with recovery rates of 40%-50% for metals such as Fe and Co (Chemical Engineering Science 302 (2025) 120858). However, the aforementioned bioleaching studies mainly focused on improving leaching efficiency by adjusting particle size or microbial adaptability. They lacked effective means to control the enrichment behavior of metal ions in solution during leaching and its impact on microbial activity. Subsequent separation processes still relied on traditional chemical methods, limiting the continuity and economy of the overall process. Furthermore, existing bioleaching processes still face key issues restricting their engineering application: bioleaching processes typically have long reaction cycles, with valuable metal purification of the microbial leachate only occurring after the reaction is complete, resulting in a lengthy processing cycle. However, as the leaching reaction proceeds, metal ions such as lithium and cobalt continuously accumulate in the leachate. High concentrations of metal ions can inhibit microbial growth and metabolic activity, thereby reducing the leaching rate and limiting the leaching depth. Furthermore, bioleaches are complex in composition, often containing both metal ions and organic metabolites, making subsequent metal separation difficult and further reducing the overall economic efficiency of the process. Membrane separation technology, based on the selective permeability of membrane materials, can achieve efficient ion separation under electric or pressure-driven conditions. It offers advantages such as continuous operation, low energy consumption, and ease of scale-up, and has been widely applied in water treatment and chemical separation. However, membrane separation technology itself is only applicable to solution systems and cannot be directly applied to solid cathode materials. Moreover, in complex solutions containing multiple metals, ion migration behavior is affected by factors such as valence competition and complexation effects, making it difficult to achieve highly selective separation of the target metal when used alone.

[0004] Therefore, although bioleaching, as a metal recovery technology that utilizes microbial metabolism to dissolve metals, has advantages over traditional pyrometallurgical or wet solvent extraction processes, such as mild reaction conditions, low energy consumption, small amount of chemical reagents, and environmental friendliness, its practical application is still constrained by many factors. These include the toxic effects of metal ions in the leachate on microorganisms, insufficient stability of the microbial strains, slow leaching reaction rate, and complex composition of the leachate, making subsequent metal separation difficult. As a result, this technology has yet to achieve large-scale, continuous industrial application. Summary of the Invention

[0005] In view of this, the present invention provides a method and system for recycling valuable metals from lithium-ion batteries. This method introduces a membrane separation unit simultaneously during the bioleaching process to achieve synergistic leaching and separation, thereby reducing the cumulative concentration of metal ions in the leachate, alleviating their inhibitory effect on microbial activity, improving overall leaching efficiency and process stability, and solving a series of reaction mechanism limitations caused by the continuous enrichment of metal ions in the leachate during bioleaching. This provides a new technical approach for the low-carbon, low-cost, and efficient recycling of valuable metals from waste lithium-ion batteries.

[0006] To address the above technical problems, the first aspect of this invention provides a method for recovering valuable metals from lithium-ion batteries, comprising the following steps: Waste battery pretreatment: The waste lithium-ion battery is fully discharged, disassembled and separated to obtain positive electrode sheets, and the positive electrode sheets are subjected to high-temperature heat treatment and pulverization in sequence to obtain positive electrode material powder. In-situ coupling reaction of bioleaching-membrane separation: The cathode material powder and microbial slurry are mixed in a bioleaching reactor and a bioleaching reaction is carried out, in which the metal components in the cathode material powder are dissolved and released into the microbial slurry. During the bioleaching reaction, the slurry is simultaneously pumped into a membrane separator, and an electric field is applied to the membrane separator to drive metal ions to selectively pass through the corresponding cation exchange membrane, resulting in a slurry with metal ions removed and a concentrate enriched with metal ions. The slurry with metal ions removed is returned to the bioleaching reactor to continue participating in the bioleaching reaction, and the concentrate is collected in a collector.

[0007] This invention employs an in-situ coupled configuration and operation mode of bioleaching and membrane separation. By in-situ coupling the bioleaching process with membrane separation technology, the membrane separation process is introduced simultaneously during the bioleaching process, allowing leaching and separation to proceed synergistically within the same system. This enables the preliminary separation of metal ions of different valence states while the metal is being dissolved, which is significantly different from the existing tandem process mode of "leaching first, then separating".

[0008] This invention effectively reduces the cumulative concentration of metal ions in the leachate slurry by utilizing the continuous action of a membrane separator during the leaching process. This mitigates the adverse effects of metal ions on microbial activity, promotes a positive leaching reaction, and significantly increases the bioleaching rate and shortens the leaching cycle. It also achieves the initial separation of lithium, cobalt, and other metal ions from the leachate slurry, demonstrating significant potential for engineering applications. By constructing an in-situ coupled bioleaching-membrane separation system, this invention features high process integration, strong operational continuity, and promising application prospects. It provides a new technical approach and implementation path for the green and efficient recovery of valuable metals, and also offers a scalable technical route for the recovery of valuable metals from metal-containing solid waste.

[0009] In conjunction with the first aspect, during the bioleaching reaction, the slurry in the bioleaching reactor can be continuously or intermittently pumped into the membrane separator, so that the bioleaching process and the membrane separation process form a cyclic coupling system.

[0010] In conjunction with the first aspect, in the pretreatment step of the waste battery, the high-temperature heat treatment specifically involves treating the positive electrode sheet at 450-550℃ for 1.5-2.5 hours to remove organic matter from the positive electrode material.

[0011] In conjunction with the first aspect, the particle size of the cathode material powder is 50-100 μm. Cathode material powder within this particle size range enables subsequent bioleaching to achieve higher reaction efficiency. The cathode sheet can be pulverized using ball milling, and the particle size can be controlled within the required range by sieving.

[0012] In conjunction with the first aspect, the reaction conditions for the bioleaching reaction are as follows: adjusting the initial pH to 1.6-2.5 and stirring at 30-40°C; the microbial slurry includes microbial inoculum and culture medium, wherein the microbial inoculum is selected from at least one of the following bacteria: Acidophilic ferrooxidizobacillus, Acidophilic sulfobacillus, and Leptospira.

[0013] In conjunction with the first aspect, the viable bacteria concentration of the microbial solution is 10. 7 -10 9 The microbial culture solution is added at a volume of 3%-5% of the culture medium volume; the positive electrode material powder accounts for 0.5%-5% of the mass percentage of the microbial slurry.

[0014] Preferably, the culture medium comprises: 3.0 g / L ammonium sulfate, 0.1 g / L potassium chloride, 0.5 g / L dipotassium hydrogen phosphate, 0.5 g / L magnesium sulfate heptahydrate, 0.01 g / L calcium nitrate, and the energy substance is ferrous sulfate heptahydrate with a concentration of 44.2 g / L.

[0015] In conjunction with the first aspect, the membrane separator includes at least one membrane stack, the membrane stack comprising a feed chamber and a concentration chamber separated by the cation exchange membrane, and electrode chambers are respectively disposed on the side of the feed chamber away from the concentration chamber and on the side of the concentration chamber away from the feed chamber, the electrode chambers being separated from adjacent feed chambers or concentration chambers by anion exchange membranes; wherein the current density of the electric field is 1.0-2.2 mA·cm. -2 The slurry in the feed chamber, after metal ions have been removed, is returned to the bioleaching reactor through a pipeline to continue participating in the bioleaching reaction.

[0016] In conjunction with the first aspect, the membrane separator includes at least two or more sets of membrane stacks arranged in parallel, with the feed chambers of adjacent membrane stacks connected in series, and the concentration chambers of different membrane stacks respectively connected to corresponding liquid collectors; the cation exchange membrane is a monovalent selective cation exchange membrane, a cobalt ion specific separation membrane, a nickel ion specific separation membrane and / or a manganese ion specific separation membrane.

[0017] The present invention also provides a system for recovering valuable metals from lithium-ion batteries, comprising: The bioleaching unit includes a bioleaching reactor and a stirring device, a temperature control device, a feed port, a liquid outlet, and a liquid inlet installed on the bioleaching reactor, for carrying out a bioleaching reaction to generate a leachate containing metal ions. A membrane separation unit, connected to the effluent outlet of the bioleaching reactor, separates metal ions in the leachate slurry. The membrane separation unit includes electrodes, a DC power supply, and at least one set of membrane stacks. Each membrane stack includes a feed chamber and a concentration chamber separated by a cation exchange membrane. Electrode chambers are respectively located on the side of the feed chamber away from the concentration chamber and on the side of the concentration chamber away from the feed chamber. These electrode chambers are separated from adjacent feed chambers or concentration chambers by anion exchange membranes. The positive and negative terminals of the DC power supply are connected to the electrodes located on both sides of the membrane stack to apply an electric field. The leachate slurry processed by the membrane separation unit is recirculated back into the bioleaching reactor, achieving cyclic leaching and separation. The electrolyte storage unit includes an electrode electrolyte storage tank and a collector. The electrode electrolyte storage tank is connected to the electrode chamber to provide electrolyte to the membrane stack and maintain charge balance. The collector is connected to the concentration chamber to circulate and enrich the metal ions separated by the membrane stack.

[0018] During the bioleaching process, a peristaltic pump continuously or intermittently introduces the leaching slurry from the bioleaching reactor into the feed chamber of the membrane stack in the membrane separation unit. The circulation rate can be 100-400 mL / min, forming a cyclically coupled system between the bioleaching and membrane separation processes. The membrane separation unit operates in electrodialysis mode, using a DC power supply to apply an electric field that drives metal ion migration. It operates under a constant current mode, with the circulating liquid in the electrode chamber being an electrolyte solution provided by the storage unit. The membrane separation unit separates metal ions and introduces them into the concentration chamber, where an acidic solution of the corresponding metal ions, pre-stored in the collector, is circulated back into the collector. Specifically, the bioleaching slurry contacts the ion exchange membrane in the feed chamber of the membrane separation unit. Under the influence of the applied electric field, metal ions with different valence states and migration characteristics selectively pass through the corresponding membrane layers, achieving in-situ migration and separation of metal ions during the leaching process. The slurry treated by the membrane separation unit is returned to the bioleaching reactor to continue participating in subsequent leaching reactions, thus constructing an in-situ coupled operation process where bioleaching and membrane separation occur simultaneously.

[0019] During the coupled operation, parameters such as membrane type combination, current density and slurry circulation flow rate can be adjusted according to the needs of the reaction system to ensure the coordinated and stable operation of the bioleaching reaction and membrane separation process.

[0020] In conjunction with the second aspect, the membrane separation unit includes at least two sets of membrane stacks arranged in parallel, with the feed chambers of adjacent membrane stacks connected in series, and the concentration chambers of different membrane stacks connected to corresponding collectors; wherein, the distance between the anion exchange membrane and the cation exchange membrane in each set of membrane stacks is 0.8-2 cm; the electrode is a titanium-based ruthenium-plated electrode; and the current density of the electric field is 1.0-2.2 mA·cm. -2 .

[0021] In conjunction with the second aspect, the electrolyte is an aqueous solution of sodium sulfate; the collector contains an initial receiving liquid, which is an acidic solution used to receive and enrich the leached metal ions.

[0022] Compared with the prior art, the present invention has the following beneficial effects: First, this invention achieves in-situ synergistic operation of bioleaching and membrane separation. By introducing a functional membrane separation unit during the leaching process, preliminary separation of metal ions with different valence states is achieved simultaneously with the dissolution of metal ions, avoiding the multi-step processing method of "leaching first, then separation" in traditional processes, and effectively simplifying the subsequent metal purification process. Second, this invention promotes the forward leaching reaction and significantly improves leaching efficiency. Through the instantaneous migration and removal of target metal ions using membrane separation technology, the cumulative concentration of metal ions in the bioleaching solution is reduced, breaking the chemical equilibrium in the traditional bioleaching system and promoting the continuous forward leaching reaction. This significantly increases the leaching rate and shortens the leaching cycle, reducing the leaching time to half of the original, which is beneficial for achieving continuous operation of the entire recovery process. Furthermore, this invention improves the utilization rate of raw materials and biomass and reduces the environmental burden. During the coupled operation, microorganisms and unreacted solid particles are effectively retained and returned to the bioleaching reactor to continue participating in the reaction, thereby improving the utilization efficiency of raw materials and biomass. At the same time, it reduces the dependence on chemical reagents such as strong acids, strong alkalis and organic extractants, thereby reducing the generation of wastewater, waste residue and waste gas from the source, and has good environmental friendliness. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the system structure for recovering valuable metals from lithium-ion batteries in an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of a set of membrane stacks in an embodiment of the present invention; In the diagram, 100 is the bioleaching unit, 101 is the bioleaching reactor, 102 is the stirring device, 103 is the temperature control device, 104 is the feed port, 105 is the liquid outlet, and 106 is the liquid inlet. 200. Membrane separation unit; 201. Electrode; 202. DC power supply; 203. Membrane stack; 300. Liquid storage unit; 301. Electrode liquid storage tank; 302. Liquid collector; 2031, Electrode chamber; 2032, Feed chamber; 2033, Concentration chamber; 2034, Cation exchange membrane; 2035, Anion exchange membrane; Figure 3 The leaching efficiency of lithium ions and cobalt ions in the embodiments of the present invention is shown.

[0024] Figure 4 The images shown are photographs of the liquid in the feed chamber in an embodiment of the present invention, wherein (a) is a photograph of the liquid in the feed chamber before an electric field is applied, and (b) is a photograph of the liquid before an electric field is applied at a current density of 2.5 mA·cm. -2 A photograph of the liquid in the feed chamber after 5 hours in an electric field.

[0025] Figure 5The figures below show the concentration changes of cobalt ions and lithium ions under different current densities in this embodiment of the invention. (a) shows the lithium ion concentration change under different current densities, (b) shows the cobalt ion concentration change under different current densities, and (c) shows the Li ion concentration change in the feed chamber under different current densities. + C t The trend of / C0 change, (d) is the Co in the feed chamber under different current density conditions. 2+ C t / C0 variation trend, (e) shows the Li at 8h under different current density conditions. + With Co 2+ The separation coefficient diagram.

[0026] Figure 6 The figures show the concentration changes of cobalt ions and lithium ions when different types of cation exchange membranes are used in the embodiments of the present invention. (a) shows the lithium ion concentration change when different types of cation exchange membranes are used; (b) shows the cobalt ion concentration change when different types of cation exchange membranes are used; and (c) shows the Li ion concentration change in the feed chamber when different types of cation exchange membranes are used. + C t / C0 variation trend, (d) is the Co in the feed chamber when using different types of cation exchange membranes. 2+ C t / C0 change trend.

[0027] Figure 7 The leaching efficiency of lithium ions and cobalt ions when using the traditional "leaching first, then separation" recovery method. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined.

[0030] Currently, in existing technologies, bioleaching and membrane separation are usually used as separate processing units: bioleaching is used for metal dissolution, and membrane separation is used for the treatment of the leached solution. However, this separate process not only makes it difficult to alleviate the inhibitory effect of metal ion enrichment on microbial activity during bioleaching, but also increases the process flow and processing cost, limiting the improvement of overall efficiency. Moreover, existing bioleaching processes have many shortcomings, mainly reflected in: (1) the bioleaching process is limited by the metabolic rate of microorganisms, the reaction cycle is generally long, and the leaching rate and leaching efficiency are low; (2) as the leaching reaction proceeds, metal ions such as lithium and cobalt are continuously enriched in the leachate. High concentrations of metal ions can easily inhibit the growth and metabolic activity of microorganisms, further reducing the leaching rate and limiting the leaching depth. (3) The composition of bioleaching solutions is complex, often containing multiple metal ions and microbial metabolites. Subsequent metal separation and purification processes are complex, resulting in a lengthy overall process and poor economic efficiency. These problems severely restrict the large-scale and continuous application of bioleaching technology in the field of waste lithium-ion battery recycling.

[0031] In view of this, the present invention provides a method and system for recycling valuable metals from lithium-ion batteries. This method and system can synergistically regulate the release and migration of metal ions during the bioleaching process, and achieve timely and selective separation of target metal ions without interfering with microbial activity, thereby improving leaching efficiency, shortening the processing cycle and reducing overall energy consumption, thus solving key technical problems in the field of green recycling of waste lithium-ion batteries.

[0032] In the following embodiments and comparative examples of this invention, the culture medium used comprises: ammonium sulfate (3.0 g / L), potassium chloride (0.1 g / L), dipotassium hydrogen phosphate (0.5 g / L), magnesium sulfate heptahydrate (0.5 g / L), and calcium nitrate (0.01 g / L). The energy source is ferrous sulfate heptahydrate (44.2 g / L). The cation exchange membrane used is an ASTOM monovalent selective cation exchange membrane (model CXP-S), and the anion exchange membrane used is an ASTOM anion exchange membrane.

[0033] In some specific embodiments, the present invention provides a system for recovering valuable metals from lithium-ion batteries, comprising: a bioleaching unit 100, a membrane separation unit 200, and a storage unit 300. (See also...) Figure 1 ,in: The bioleaching unit 100 includes a bioleaching reactor 101 and a stirring device 102, a temperature control device 103, a feed port 104, a liquid outlet 105 and a liquid inlet 106 disposed on the bioleaching reactor 101, for carrying out a bioleaching reaction to generate a leachate containing metal ions.

[0034] The membrane separation unit 200 is connected to the outlet 105 of the bioleaching reactor 101 to separate metal ions in the leaching slurry. The membrane separation unit includes an electrode 201, a DC power supply 202, and a membrane stack 203. The positive and negative terminals of the DC power supply 202 are respectively connected to the electrodes 201 arranged on both sides of the membrane stack 203 to apply an electric field. The leaching slurry processed by the membrane separation unit 200 is returned to the bioleaching reactor 101 to achieve cyclic leaching and separation.

[0035] Please see Figure 2 The membrane stack 203 includes a feed chamber 2032 and a concentration chamber 2033 separated by a cation exchange membrane 2034. Electrode chambers 2031 are respectively arranged on the side of the feed chamber 2032 away from the concentration chamber 2033 and on the side of the concentration chamber 2033 away from the feed chamber 2032. The electrode chambers 2031 are separated from the adjacent feed chamber 2032 or concentration chamber 2033 by anion exchange membranes 2035. The chambers are separated by ion exchange membranes and acrylic partitions (1 cm thick) on both sides of the fixed membrane. The effective membrane contact area of ​​each chamber is 20 cm². 2 Each chamber has a volume of 20 cm³. 3 .

[0036] The liquid storage unit 300 includes an electrode liquid storage tank 301 and a liquid collector 302. The electrode liquid storage tank 301 is connected to the electrode chamber of the membrane stack 203 to provide electrolyte to the membrane stack 203 and maintain charge balance. The liquid collector 302 is connected to the concentration chamber of the membrane stack 203 to circulate and enrich the metal ions separated by the membrane stack 203.

[0037] In some specific embodiments, the present invention provides a method for recovering valuable metals from lithium-ion batteries, implemented using the aforementioned system for recovering valuable metals from lithium-ion batteries, and the specific steps include: Pre-treatment of used batteries: Waste lithium cobalt oxide batteries are fully discharged, disassembled and separated to obtain positive electrode sheets. The positive electrode sheets are heat-treated at 500℃ for 2 hours to remove PVDF binder, and then ball-milled to a particle size of less than 75μm to obtain positive electrode material powder.

[0038] In-situ coupling reaction of bioleaching-membrane separation: Add 2.5g of the obtained positive electrode material powder to a 1L bioleaching reactor, and add 10mL of *Thiobacillus acidophilus* bacterial solution (cell concentration 10). 8 The slurry was prepared with 250 mL of culture medium and the initial pH of the slurry was adjusted to 2.5. The temperature was maintained at 35°C and the mixture was stirred to carry out the bioleaching reaction, so that the lithium ions and cobalt ions in the positive electrode material were dissolved and released into the slurry.

[0039] During the bioleaching reaction, the slurry was continuously pumped into the feed chamber of the membrane stack at a flow rate of 200 mL / min. A constant current of 2.0 mA·cm⁻¹ was applied for 8 hours starting at the 72nd hour. -2 The process drives lithium ions to selectively pass through the cation exchange membrane, yielding a lithium-ion-depleted slurry and a lithium-ion-enriched concentrate. The lithium-ion-depleted slurry is recycled back to the bioleaching reactor to continue the bioleaching reaction, while the concentrate is collected in a collector. The electrode solution storage tank is pre-filled with 0.1 mol / L Na₂SO₄ solution, forming a circulation with the electrode chambers of the membrane stack to maintain charge balance. The collector is pre-filled with initial Li₂SO₄ solution. + A 100 mg / L Li2SO4 solution is circulated with the concentration chamber of the membrane stack, which ultimately enriches the lithium ions that have passed through the cation exchange membrane into the concentration chamber and into the collector.

[0040] After 168 hours of in-situ coupled bioleaching-membrane separation reaction, 2 mL of solution was taken from the concentration chamber, filtered, and diluted to an appropriate concentration. The concentrations of lithium and cobalt ions were then determined using atomic absorption spectrometry. The results showed that the leaching rates of both lithium and cobalt ions reached over 90%. (Specific details are as follows...) Figure 3 As shown.

[0041] During the research, the inventors also studied the effect of the applied electric field current density on the separation effect. These experiments were still conducted using the aforementioned system for recovering valuable metals from lithium-ion batteries, with five sets of experimental devices set up in parallel. The specific steps included: Pre-treatment of waste batteries: Same as the above embodiments, and will not be repeated.

[0042] In-situ coupling reaction of bioleaching-membrane separation: Add 2.5g of the obtained positive electrode material powder to a 1L bioleaching reactor, and add 10mL of *Thiobacillus acidophilus* bacterial solution (cell concentration 10). 8 The slurry was prepared with 250 mL of culture medium and the initial pH of the slurry was adjusted to 2.5. The temperature was maintained at 35°C and the mixture was stirred to carry out the bioleaching reaction, so that the lithium ions and cobalt ions in the positive electrode material were dissolved and released into the slurry.

[0043] During the bioleaching reaction, the slurry was continuously pumped into the feed chamber of the membrane stack at a flow rate of 200 mL / min. A constant current was applied for 8 hours starting at the 72nd hour, with the current density set at 0.5 mA·cm⁻¹. -2 1.0mA·cm -2 1.5 mA·cm -2 2.0 mA·cm -2 and 2.5 mA·cm-2 The subsequent steps are the same as in the above embodiments and will not be repeated. The effect of current density on the separation effect of the leachate was investigated. Experimental results show that at a current density of 1.0-2.0 mA·cm⁻¹, the separation effect is significantly better. -2 Within this range, the separation coefficients of lithium ions and cobalt ions are both above 35, enabling preliminary separation of lithium ions and cobalt ions in bioleaching solutions, with a current density of 2.0 mA / cm². -2 The separation efficiency of lithium ions and cobalt ions was best at 2.5 mA·cm⁻¹, reaching 97.35%; while the separation efficiency was best at a current density of 2.5 mA·cm⁻¹. -2 At that time, after applying an electric field in the feed chamber for 5 hours, a distinct blue-green precipitate was observed to form (e.g. Figure 4 (b) shows that at this time, the feed chamber Co 2+ The concentration dropped sharply, and even some Co... 2+ The sediment migrates to the concentration chamber, where most of it precipitates, resulting in a lower separation coefficient and the worst separation performance. See details... Figure 5 (a) ~ (e), where Figure 5 In the legends (a) to (d), the letters “F” and “P” after the numbers represent the “feed chamber” and “concentration chamber” in the membrane stack, respectively.

[0044] During the research, the inventors also studied the effect of the ion exchange membrane used on the separation effect. These experiments were still carried out using the aforementioned system for recovering valuable metals from lithium-ion batteries, with three sets of experimental devices set up in parallel. The specific steps included: Pre-treatment of waste batteries: Same as the above embodiments, and will not be repeated.

[0045] In-situ coupling reaction of bioleaching-membrane separation: Add 2.5g of the obtained positive electrode material powder to a 1L bioleaching reactor, and add 10mL of *Thiobacillus acidophilus* bacterial solution (cell concentration 10). 8 The slurry was prepared with 250 mL of culture medium and the initial pH of the slurry was adjusted to 2.5. The temperature was maintained at 35°C and the mixture was stirred to carry out the bioleaching reaction, so that the lithium ions and cobalt ions in the positive electrode material were dissolved and released into the slurry.

[0046] During the bioleaching reaction, the slurry was continuously pumped into the feed chamber of the membrane stack at a flow rate of 200 mL / min. The cation exchange membranes used in the membrane stack were ASTOM (CXP-S), Tianwei (C1S70), and Tianwei (C2S70). The separation effect of different monovalent selective cation exchange membranes on the bioleach slurry was investigated. The results showed that the ASTOM (CXP-S) monovalent selective cation exchange membrane had the best separation effect on the leachate. (See details...) Figure 6 (a) ~ (d), where Figure 6In the legends (a) and (b), the letters “F” and “P” after the numbers represent the “feed chamber” and “concentration chamber” in the membrane stack, respectively.

[0047] Comparative Example This comparative example uses a traditional bioleaching method to leach lithium ions and cobalt ions from lithium cobalt oxide batteries, as detailed below: Pre-treatment of waste batteries: The processing steps are the same as those in the above embodiments, and will not be repeated.

[0048] Bioleaching reaction: Add 2.5g of the obtained positive electrode material powder to a 1L bioleaching reactor, and add 10mL of *Thiobacillus acidophilus* bacterial solution (cell concentration 10). 8 The slurry was prepared with 250 mL of culture medium and the initial pH of the slurry was adjusted to 2.5. The temperature was maintained at 35°C and the mixture was stirred to carry out the bioleaching reaction, so that the lithium ions and cobalt ions in the positive electrode material were dissolved and released into the slurry.

[0049] Fourteen days after the start of the leaching reaction, the leaching rates of lithium and cobalt ions in the bioleaching solution were tested. The highest leaching rate of lithium ions was only 71.43%, while in the embodiment of this invention, the leaching rate of lithium ions reached as high as 96.25% on the 7th day of the reaction (see details). Figure 7 This indicates that the in-situ coupled bioleaching and membrane separation recovery method provided by the present invention can significantly improve leaching efficiency, shorten the leaching cycle, and has good application potential.

[0050] In summary, the method for recovering valuable metals by in-situ coupling bioleaching and membrane separation technology provided by this invention achieves simultaneous leaching and separation by introducing a membrane separation unit during the bioleaching process. During leaching, the selective migration characteristics of ion exchange membranes for different metal ions are utilized to continuously remove some leaching products, reducing the cumulative concentration of metal ions in the bioleaching solution and thus mitigating their inhibitory effect on microbial activity. Simultaneously, the in-situ removal of metal ions disrupts the chemical equilibrium of the traditional leaching system, promoting the leaching reaction in the forward direction, accelerating the bioleaching kinetics, improving leaching efficiency and process stability, and ultimately achieving low-carbon, low-cost, and efficient separation and recovery of valuable metals from waste lithium-ion batteries.

[0051] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for recovering valuable metals from lithium-ion batteries, characterized in that, Includes the following steps: Waste battery pretreatment: The waste lithium-ion battery is fully discharged, disassembled and separated to obtain positive electrode sheets, and the positive electrode sheets are subjected to high-temperature heat treatment and pulverization in sequence to obtain positive electrode material powder. In-situ coupling reaction of bioleaching-membrane separation: The cathode material powder and microbial slurry are mixed in a bioleaching reactor and the bioleaching reaction is carried out continuously, in which the metal components in the cathode material powder are dissolved and freed in the microbial slurry. During the bioleaching reaction, the slurry is pumped into a membrane separator simultaneously and continuously. An electric field is applied to the membrane separator to drive the dissolved metal ions to selectively pass through the corresponding cation exchange membrane, thereby obtaining a slurry with metal ions removed and a concentrate with metal ions enriched, reducing the cumulative concentration of metal ions in the microbial slurry and alleviating the inhibitory effect of metal ions on microbial activity. The slurry from which metal ions have been removed is returned to the bioleaching reactor to continue participating in the bioleaching reaction, and the concentrate is collected in a collector. The membrane separator includes at least one membrane stack, which comprises a feed chamber and a concentration chamber separated by the cation exchange membrane. Electrode chambers are respectively disposed on the side of the feed chamber away from the concentration chamber and on the side of the concentration chamber away from the feed chamber. The electrode chambers are respectively separated from adjacent feed chambers or concentration chambers by anion exchange membranes. The current density of the electric field is 1.0-2.2 mA·cm⁻¹. -2 .

2. The method for recovering valuable metals from lithium-ion batteries as described in claim 1, characterized in that, In the waste battery pretreatment step, the high-temperature heat treatment specifically involves treating the positive electrode sheet at 450-550℃ for 1.5-2.5 hours to remove organic matter from the positive electrode material.

3. The method for recovering valuable metals from lithium-ion batteries as described in claim 1, characterized in that, The particle size of the positive electrode material powder is 50-100 μm.

4. The method for recovering valuable metals from lithium-ion batteries as described in claim 1, characterized in that, The reaction conditions for the bioleaching reaction are as follows: adjust the initial pH to 1.6-2.5 and stir at 30-40℃; The microbial slurry includes a microbial inoculum and a culture medium, wherein the microbial inoculum is selected from at least one of the following bacteria: Acidobacterium ferrooxidans, Acidobacterium sulfideum, and Leptospira.

5. The method for recovering valuable metals from lithium-ion batteries as described in claim 4, characterized in that, The viable bacteria concentration of the microbial culture solution is 10. 7 -10 9 The microbial culture solution is added at a volume of 3%-5% of the culture medium volume; and / or The positive electrode material powder accounts for 0.5%-5% of the mass of the microbial slurry.

6. The method for recovering valuable metals from lithium-ion batteries as described in claim 1, characterized in that, The membrane separator includes two or more sets of membrane stacks arranged in parallel, with the feed chambers of adjacent membrane stacks connected in series, and the concentration chambers of different membrane stacks connected to corresponding liquid collectors. The cation exchange membrane is a monovalent selective cation exchange membrane, a cobalt ion specific separation membrane, a nickel ion specific separation membrane, and / or a manganese ion specific separation membrane.

7. A system for recovering valuable metals from lithium-ion batteries, characterized in that, A method for implementing the recovery of valuable metals from lithium-ion batteries according to any one of claims 1 to 6, comprising: The bioleaching unit includes a bioleaching reactor and a stirring device, a temperature control device, a feed port, a liquid outlet, and a liquid inlet installed on the bioleaching reactor, for carrying out a bioleaching reaction to generate a leachate containing metal ions. A membrane separation unit, connected to the effluent outlet of the bioleaching reactor, separates metal ions in the leachate slurry. The membrane separation unit includes electrodes, a DC power supply, and at least one set of membrane stacks. Each membrane stack includes a feed chamber and a concentration chamber separated by a cation exchange membrane. Electrode chambers are respectively located on the side of the feed chamber away from the concentration chamber and on the side of the concentration chamber away from the feed chamber. These electrode chambers are separated from adjacent feed chambers or concentration chambers by anion exchange membranes. The positive and negative terminals of the DC power supply are connected to the electrodes located on both sides of the membrane stack to apply an electric field. The leachate slurry processed by the membrane separation unit is recirculated back into the bioleaching reactor, achieving cyclic leaching and separation. The electrolyte storage unit includes an electrode electrolyte storage tank and a collector. The electrode electrolyte storage tank is connected to the electrode chamber to provide electrolyte to the membrane stack and maintain charge balance. The collector is connected to the concentration chamber to circulate and enrich the metal ions separated by the membrane stack.

8. The system for recovering valuable metals from lithium-ion batteries as described in claim 7, characterized in that, The membrane separation unit includes two or more sets of membrane stacks arranged in parallel, with the feed chambers of adjacent membrane stacks connected in series, and the concentration chambers of different membrane stacks connected to corresponding liquid collectors; wherein, the distance between the anion exchange membrane and the cation exchange membrane in each set of membrane stacks is 0.8-2 cm; The electrode is a titanium-based ruthenium-plated electrode; The current density of the electric field is 1.0-2.2 mA·cm. -2 .

9. The system for recovering valuable metals from lithium-ion batteries as described in claim 7, characterized in that, The electrolyte is an aqueous solution of sodium sulfate; the collector contains an initial receiving solution, which is an acidic solution used to receive and enrich the leached metal ions.

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