Lithium battery precious metal recovery method based on microorganism-electrochemical coupling and unidirectional membrane separation

Abstract

The invention discloses a lithium battery precious metal recovery method based on microorganism-electrochemical coupling and one-way membrane separation, which comprises the following steps: step 1, pretreatment of a waste lithium battery: performing complete discharge treatment on the waste lithium battery, then disassembling the battery in an oxygen-free environment, separating out a positive electrode material and a negative electrode material, and drying the positive electrode material and the negative electrode material; electrode material black powder containing precious metal is obtained; 2, designing an anaerobic tank, and culturing and domesticating an acid-producing electroactive flora; 3, continuously and stably adding black powder into the anaerobic tank; copper electrodes are added to the two sides of the cylindrical anaerobic tank and the center of the one-way membrane, a power source is connected, the positive electrode is connected with the electrodes on the two sides of the anaerobic tank, and the negative electrode is connected with the membrane center electrode. Compared with the prior art, the method has the advantages that the solid-to-liquid ratio of microbiological leaching can be greatly increased through microbiological-electrochemical coupling and one-way membrane separation, the transfer efficiency of precious metal electrons is accelerated, anaerobic flora is protected, poison to the anaerobic flora is reduced, and the service life of equipment is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of waste lithium battery recycling, and in particular to a method for recycling precious metals from lithium batteries based on microbial-electrochemical coupling and unidirectional membrane separation. Background Art

[0002] With the widespread use and gradual retirement of lithium-ion batteries, the demand for recycling used lithium batteries is increasing. The black powder obtained after pre-processing of used lithium batteries is rich in precious metals such as lithium, cobalt, nickel, and manganese. Efficiently recovering the precious metal components in black powder not only reduces environmental pollution but also alleviates the pressure of strategic resource shortages. Currently, microbial leaching technology is gradually becoming an environmentally friendly and economical method for black powder recovery. This technology utilizes the inorganic / organic acids produced during microbial growth and metabolism to leach metal ions from black powder, thereby achieving green and low-carbon separation and recovery of metals.

[0003] However, the existing microbial leaching process for precious metal recovery has some bottlenecks: (1) Under high solid-liquid ratio conditions, the concentration of heavy metals in the leachate will increase, which will have a toxic effect on microorganisms, resulting in a decrease in bacterial activity and thus a reduction in metal leaching efficiency; (2) When the metal concentration exceeds the tolerance range of microorganisms, not only will the leaching process stagnate, but it may also destroy the bacterial structure, causing it to lose its regeneration ability, increasing operating costs and the difficulty of waste liquid treatment. Therefore, due to the limitations of the above problems, traditional methods can usually only operate under low solid-liquid ratio conditions, with low single-treatment efficiency and long metal ion recovery cycles. Summary of the Invention

[0004] The present invention aims to overcome these technical limitations by providing a method for microbial recovery of precious metals from various types of high-solid-to-liquid ratio waste lithium batteries, particularly ternary lithium-ion batteries containing metals such as cobalt, nickel, and manganese. This method is widely applicable to battery recycling companies, biometallurgical research institutions, and environmental protection facilities.

[0005] In order to solve the above problems, the technical solution of the present invention is: a method for recovering precious metals from lithium batteries based on microbial-electrochemical coupling and unidirectional membrane separation, comprising the following steps:

[0006] Step 1: Pretreatment of used lithium batteries: First, the used lithium batteries are completely discharged to ensure safety. Then, the batteries are disassembled in an oxygen-free environment to separate the positive electrode material and the negative electrode material to obtain black powder containing precious metals;

[0007] Step 2: Design of anaerobic tank and cultivation and acclimation of acid-producing electroactive bacteria: The anaerobic tank is a cylindrical closed container, equipped with a stirring device, and a membrane assembly installed in the anaerobic tank. A one-way membrane is used, and the one-way membrane includes a cation exchange membrane, a selective ion membrane, and an electrolyte membrane. The pore size of the one-way membrane is microfiltration or nanofiltration. The pumped water of the one-way membrane assembly is a biological culture solution containing heavy metal ions. The culture solution is precipitated and separated in a sedimentation tank. Deoxygenated liquid culture medium is added to the anaerobic tank to 70%-90% of the total volume, and the acid-producing electroactive bacteria are inoculated;

[0008] Step 3: Continuously and stably add black powder to the anaerobic tank; regularly sample the culture solution to measure the absorbance change to reflect the growth and decline of the electroactive population, and use inductively coupled plasma optical emission spectrometry (ICP-OES) to measure the change in heavy metal ion concentration. After 7-10 days of culture, the electroactive bacteria enter the late logarithmic growth phase and the heavy metal ion concentration reaches its highest level. During this period, the water inlet pump is simultaneously turned on to input fresh culture solution containing black powder and glucose into the anaerobic tank, and the inlet and outlet water volumes are kept balanced. The changes in the density of the electroactive bacteria, the heavy metal ion concentration, and the TOC concentration in the inlet and outlet water in the anaerobic tank are monitored. After 7-10 days of continuous operation, the density of the electroactive bacteria, the heavy metal ion concentration, and the TOC conversion rate in the inlet and outlet water reach their highest levels and are in balance.

[0009] Step 4: Insertion of electrodes in the anaerobic tank: Add copper electrodes on both sides of the cylindrical anaerobic tank and in the center of the one-way membrane, connect the power supply, connect the positive electrode to the electrodes on both sides of the anaerobic tank, and the negative electrode to the electrode in the center of the membrane.

[0010] Furthermore, the stirring device is used for slow stirring of the anaerobic tank by upward stirring or downward stirring, the stirring speed is 10-30 rpm, and the temperature of the anaerobic tank is controlled to be 20-40°C by electric heating, circulating water heating or steam heating.

[0011] Furthermore, the unidirectional membrane is made of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or one or more of an organic membrane, an inorganic membrane and a composite ceramic membrane.

[0012] Furthermore, the acid-producing electroactive bacterial community includes Shewanella and Geobacter (such as Shewanella spp., Lacticaseibacillus, Geobactersulfurreducens), which are cultured in a specific culture medium, gradually increasing the content of the waste lithium battery positive electrode material, acclimating and cultivating the bacterial community and forming a stable bacterial community.

[0013] The advantages of the present invention compared with the existing technology are:

[0014] The present invention greatly increases the concentration of electroactive bacteria in the anaerobic tank reactor through the efficient interception effect of the membrane and the regulation of nutrient culture conditions, isolates the direct contact between the electroactive bacteria and toxic metal ions, not only eliminates the toxicity of toxic metals to the electroactive bacteria but also increases the yield of heavy metal ions, significantly improves the leaching efficiency of heavy metals, and greatly improves the stability of system operation.

[0015] Under high solid-liquid ratio conditions, heavy metal ions are quickly removed and the leaching process can maintain high efficiency, breaking through the application bottleneck problem of limited solid-liquid ratio in traditional microbial leaching methods;

[0016] By electrochemically driving cation migration, the accumulation and clogging of the membrane surface are reduced, the risk of membrane fouling is reduced, and the service life of the device is extended. The introduction of the electric field accelerates the transfer rate of metal cations and pushes the anionic extracellular polymers to both sides, significantly reducing the risk of clogging of the unidirectional membrane.

[0017] Electrochemical promotion technology accelerates the migration of metal cations and improves the recovery rate; by introducing an external electric field, the migration speed of metal cations is enhanced, allowing precious metals to be released from black powder more quickly, thereby improving overall processing capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a line graph of the metal leaching efficiency of the electroactive bacterial community in the lithium battery precious metal recovery method based on microbial-electrochemical coupling and unidirectional membrane separation of the present invention for NCM523 black powder with different concentrations.

[0019] Figure 2 It is a schematic diagram of a high-efficiency electrochemically coupled anaerobic membrane bioreactor of the lithium battery precious metal recovery method based on microbial-electrochemical coupling and unidirectional membrane separation of the present invention.

[0020] Figure 3 This is a schematic diagram of a multi-layer membrane structure microbial electrochemical system of the lithium battery precious metal recovery method based on microbial-electrochemical coupling and unidirectional membrane separation of the present invention. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0022] It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to directions in the accompanying drawings, and the words "inside" and "outside" refer to directions toward or away from the geometric center of a specific component, respectively.

[0023] In order to make the contents of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0024] like Figures 1 to 3 As shown, the lithium battery precious metal recovery method based on microbial-electrochemical coupling and unidirectional membrane separation includes the following steps:

[0025] Step 1: Pretreatment of used lithium batteries: First, the used lithium batteries are completely discharged to ensure safety. Then, the batteries are disassembled in an oxygen-free environment to separate the positive electrode material and the negative electrode material to obtain black powder containing precious metals;

[0026] Step 2: Design of anaerobic tank and cultivation and acclimation of acid-producing electroactive bacteria: The anaerobic tank is a cylindrical closed container, and is equipped with a stirring device. The stirring device stirs upward or downward for slow stirring of the anaerobic tank, and the stirring speed is 10-30 rpm. The temperature of the anaerobic tank is controlled by electric heating, circulating water heating or steam heating to be 20-40°C. The anaerobic tank is equipped with a built-in membrane assembly and uses a one-way membrane. The material of the one-way membrane is polytetrafluoroethylene, polyvinylidene fluoride, polypropylene or ceramic organic, One or more inorganic or composite membranes, the one-way membrane includes a cation exchange membrane, a selective ion membrane, and an electrolyte membrane. The pore size of the one-way membrane is microfiltration or nanofiltration. The pumped water of the one-way membrane assembly is a biological culture solution containing heavy metal ions. The culture solution is precipitated and separated by a sedimentation tank. Deoxygenated liquid culture medium is added to the anaerobic tank to 70%-90% of the total volume. Acid-producing electroactive bacteria are inoculated. The acid-producing electroactive bacteria include Shewanella, lactic acid bacteria, and Geobacter (such as Shewanella spp., Lacticaseibacillus, and Geobactersulfurreducens). The bacteria are cultured in a specific culture medium, and the content of the cathode material of the waste lithium battery is gradually increased. The bacteria are acclimated and cultured to form a stable bacterial community.

[0027] Step 3: Continuously and stably add black powder to the anaerobic tank; regularly sample the culture solution to measure the absorbance change to reflect the growth and decline of the electroactive population, and use inductively coupled plasma optical emission spectrometry (ICP-OES) to measure the change in heavy metal ion concentration. After 7-10 days of culture, the electroactive bacteria enter the late logarithmic growth phase and the heavy metal ion concentration reaches its highest level. During this period, the water inlet pump is simultaneously turned on to input fresh culture solution containing black powder and glucose into the anaerobic tank, and the inlet and outlet water volumes are kept balanced. The changes in the density of the electroactive bacteria, the heavy metal ion concentration, and the TOC concentration in the inlet and outlet water in the anaerobic tank are monitored. After 7-10 days of continuous operation, the density of the electroactive bacteria, the heavy metal ion concentration, and the TOC conversion rate in the inlet and outlet water reach their highest levels and are in balance.

[0028] Step 4: Insertion of electrodes in the anaerobic tank: Add copper electrodes on both sides of the cylindrical anaerobic tank and in the center of the one-way membrane, connect the power supply, connect the positive electrode to the electrodes on both sides of the anaerobic tank, and the negative electrode to the electrode in the center of the membrane.

[0029] In specific applications, implementation case 1: leaching of electroactive microorganisms, electroactive microorganisms were inoculated into a membrane bioreactor with an effective volume of 100L and a polytetrafluoroethylene microfiltration membrane with a pore size of 0.22μm. The culture medium in the reactor used a specific culture medium, with a certain amount of glucose added as a carbon source, and waste lithium battery black powder with different solid-liquid ratios (5%-20%, w / v) was added. The reactor was operated at 30°C, with a stirring rate of 30rpm and anaerobic conditions maintained constant. The reaction was cultured continuously for 7 days.

[0030] like Figure 1 As shown, during the reaction, the pH of the reaction solution rapidly decreased from an initial 7.0 to approximately 2.0 and remained stable, indicating enhanced microbial acid metabolism. Simultaneously, the leaching efficiency of metal ions increased rapidly. Leaching rates for metals such as Ni, Co, Mn, and Li in the black powder exceeded 80% after the ninth day and reached near saturation by the 12th day, with a leaching rate approaching 100%. In the control group, which lacked electroactive microorganisms, the metal dissolution rate was less than 20%, demonstrating that the electroactive bacteria played a significant role in promoting metal ion migration and release.

[0031] Implementation Case 2: Construction of anaerobic tank: a 50L cylindrical anaerobic membrane bioreactor was built. The main body was made of polypropylene, and a cation selective membrane component (Nafion membrane, pore size of about 0.01μm) was installed inside. A three-electrode system ( Figure 2-3 ): Copper electrodes are located on both sides of the membrane, and a graphite rod is located in the center of the membrane. The system maintains a constant voltage of 0.8-1.5V. The reactor is equipped with low-speed stirring (25 rpm), an external circulating water bath with temperature control (30°C), and is inoculated with electroactive bacteria. Anaerobic conditions are established through nitrogen purging, resulting in a compact and stable system.

[0032] Implementation Case 3: Effect of Different One-Way Membranes on Leaching Efficiency To compare the effects of different one-way membranes on system operation, three materials, cation exchange membrane (Nafion), polyamide selective ion membrane, and phosphate-based electrolyte membrane, were selected. The membranes were operated under the same reaction conditions for 7 days and evaluated in terms of leached metal concentration, membrane damage degree, and microbial activity.

[0033] Implementation Case 4: Effect of different electrodes on leaching efficiency To evaluate the effect of electrode materials on the leaching efficiency of precious metals, graphite rods, stainless steel (SS316), titanium-based platinum coating (Pt / Ti) and copper electrodes were selected to conduct leaching tests under the same microbial, voltage and membrane system conditions, and the efficiency of metal ion leaching was evaluated.

[0034] The present invention and its embodiments are described above. This description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs structures and embodiments similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A lithium battery precious metal recovery method based on microbial-electrochemical coupling and unidirectional membrane separation, characterized by: The following steps are involved: Step 1: Pretreatment of used lithium batteries: First, the used lithium batteries are completely discharged to ensure safety. Then, the batteries are disassembled in an oxygen-free environment to separate the positive electrode material and the negative electrode material to obtain black powder containing precious metals; Step 2: Design of anaerobic tank and cultivation and acclimation of acid-producing electroactive bacteria: The anaerobic tank is a cylindrical closed container, equipped with a stirring device, and a built-in membrane assembly. A one-way membrane is used. The one-way membrane includes a cation exchange membrane, a selective ion membrane, and an electrolyte membrane. The pore size of the one-way membrane is microfiltration or nanofiltration. The pumped water of the one-way membrane assembly is a biological culture solution containing heavy metal ions. The culture solution is precipitated and separated in a sedimentation tank. Deoxygenated liquid culture medium is added to the anaerobic tank to 70%-90% of the total volume, and the acid-producing electroactive bacteria are inoculated; Step 3: Continuously and stably add black powder to the anaerobic tank; regularly sample and measure the absorbance changes of the culture solution to reflect the growth and decline of the electroactive population, and use inductively coupled plasma emission spectrometry to measure the changes in heavy metal ion concentration. After 7-10 days of culture, the electroactive bacteria enter the late logarithmic growth phase and the heavy metal ion concentration reaches its highest level. During this period, the water inlet pump is simultaneously turned on to input fresh culture solution containing black powder and glucose into the anaerobic tank, and the inlet and outlet water volumes are kept balanced. The changes in the density of the electroactive bacteria, the changes in the heavy metal ion concentration, and the changes in the TOC concentration in the inlet and outlet water in the anaerobic tank are monitored. After 7-10 days of continuous operation, the density of the electroactive bacteria, the heavy metal ion concentration, and the TOC conversion rate in the inlet and outlet water reach their highest levels and are in balance. Step 4: Insertion of electrodes in the anaerobic tank: Add copper electrodes on both sides of the cylindrical anaerobic tank and in the center of the one-way membrane, connect the power supply, connect the positive electrode to the electrodes on both sides of the anaerobic tank, and the negative electrode to the electrode in the center of the membrane.

2. The method for recovering precious metals from lithium batteries based on microbial-electrochemical coupling and unidirectional membrane separation according to claim 1, characterized in that: The stirring device is used for slow stirring of the anaerobic tank by upward stirring or downward stirring, and the stirring speed is 10-30 rpm. The temperature of the anaerobic tank is controlled to be 20-40° C. by electric heating, circulating water heating or steam heating.

3. The method for recovering precious metals from lithium batteries based on microbial-electrochemical coupling and unidirectional membrane separation according to claim 1, characterized in that: The material of the unidirectional membrane is one or more of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene or ceramic organic, inorganic or composite membrane.

4. The method for recovering precious metals from lithium batteries based on microbial-electrochemical coupling and unidirectional membrane separation according to claim 1, characterized in that: The acid-producing electroactive bacterial community includes Shewanella, lactic acid bacteria, and Geobacter (such as Shewanella spp., Lactic acideibacillus, and Geobactersulfurreducens), which are cultured in a specific culture medium, and the content of the waste lithium battery positive electrode material is gradually increased to acclimate the bacterial community and form a stable bacterial community.

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