Leaching method and recycling method of metal in lithium manganate positive plate

Abstract

The invention provides a leaching method and a recycling method of metal in a lithium manganate positive plate. The leaching method comprises the following steps: pre-treating a lithium manganate positive plate disassembled from a waste battery to obtain positive powder; the method comprises the following steps: preparing initial biomass sulfuric acid containing thiobacillus thiooxidans, diluting the initial biomass sulfuric acid into a first biomass sulfuric acid solution with the concentration of 30-50g / L and a second biomass sulfuric acid solution with the concentration of 15-25g / L respectively, and leaching the positive electrode powder by adopting the first biomass sulfuric acid solution and the second biomass sulfuric acid solution. The leaching treatment comprises a step S1 and a step S2 which is repeated for N-1 times. The step S1 comprises the following steps: mixing a first biomass sulfuric acid solution and positive electrode powder in a shaking table for a first time, and centrifuging out bacterial metabolites to obtain a first filtrate; the step S2 comprises the steps of mixing the second biomass sulfuric acid solution and the (N-1) th filtrate in the shaking table for the Nth time and then centrifuging bacterial metabolites to obtain the Nth filtrate, wherein N is an integer greater than or equal to 2 and less than or equal to 10.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling and utilization of lithium-ion batteries, in particular to the recycling and utilization of cathode materials, and more particularly to a method for leaching and recycling metals in lithium manganate cathode sheets. Background Art

[0002] With the rapid industrialization of new energy vehicles, their sales volume will increase by leaps and bounds, and the inventory of lithium-ion batteries will also increase geometrically. At the same time, the environmental pollution problem of waste lithium-ion batteries and the problem of reasonable resource recycling have become common concerns and urgent problems to be solved in the current industry.

[0003] Currently, the main substances recovered from waste lithium-ion batteries are the negative electrode current collector (commonly copper foil), the positive electrode current collector (commonly aluminum foil), the positive electrode active material, and the negative electrode active material. Among them, the recovery of the positive electrode active material mainly has two methods: the wet process and the pyrometallurgical process. The wet process has become the mainstream recovery solution due to its mild conditions and low energy consumption. It mainly includes pretreatment, leaching, recovery and other links.

[0004] Pretreatment is mainly to selectively separate the higher-value cathode material, remove the slightly lower-value components or organic solvents, and reduce the adverse effects in the subsequent leaching process. The main methods include discharging, crushing, dissolving, pyrolysis, etc. Leaching is mainly a process of selectively extracting and recovering various metals from the cathode material obtained by pretreatment. The main methods include wet leaching, microbial leaching, water leaching, etc. Recovery is a process of recovering various metal ions from the leaching solution by extraction, precipitation, electrochemistry and other methods. Among them, the leaching process is the key step in the recovery of cathode materials, and the leaching rate directly affects the subsequent recovery rate.

[0005] The wet leaching of waste lithium-ion battery cathode materials is mainly an acid leaching scheme, and the most common leaching system is inorganic acid (sulfuric acid, hydrochloric acid or nitric acid) + hydrogen peroxide. The combination of inorganic acid + hydrogen peroxide can leach the cathode material well, but the inorganic acid has strong corrosiveness, high requirements for equipment, and is prone to generate harmful gases. Water leaching is to convert the cathode material obtained by pretreatment into lithium carbonate components by reduction roasting, and then water leach / carbonated water leach to recover lithium first. The water leaching of lithium elements in waste materials has the characteristics of high efficiency and easy product treatment, but most of them require roasting treatment, and this link still has the disadvantages of slightly high energy consumption and easy pollution. Therefore, both acid leaching and water leaching have high requirements for energy consumption and post-treatment of chemical reagents.

[0006] Microbial leaching utilizes the complexation, reduction, oxidation, leaching and other effects of certain specific microorganisms and their metabolites to achieve the purpose of recovering and dissolving valuable metals. Although microbial leaching has advantages such as environmental friendliness, low cost, and low acid consumption, it also has deficiencies such as long leaching cycle and low efficiency. Therefore, it is necessary to further improve microbial leaching to improve its leaching efficiency. Summary of the Invention

[0007] Based on the above problems, the purpose of the present invention is to provide a method for leaching and recovering metals in a lithium manganate-based positive electrode sheet. This leaching method is a microbial leaching method for leaching metals in a lithium manganate-based positive electrode sheet, with a high leaching rate and a short required leaching time.

[0008] To achieve the above purpose, the first aspect of the present invention provides a method for leaching metals in a lithium manganate-based positive electrode sheet, including:

[0009] (1) Preparation of materials

[0010] The lithium manganate-based positive electrode sheet disassembled from a waste battery is pretreated to obtain positive electrode powder.

[0011] (2) Biological leaching

[0012] Prepare an initial biomass sulfuric acid containing Thiobacillus thiooxidans, and dilute the initial biomass sulfuric acid to a first biomass sulfuric acid solution and a second biomass sulfuric acid solution with concentrations of 30-50 g / L and 15-25 g / L respectively. Use the first biomass sulfuric acid solution and the second biomass sulfuric acid solution to leach the positive electrode powder. The leaching treatment includes one step S1 and N-1 repeated steps S2. Step S1 includes mixing the first biomass sulfuric acid solution and the positive electrode powder in a shaker for a first time, centrifuging to obtain bacterial metabolites, and obtaining a first filtrate. Step S2 includes mixing the second biomass sulfuric acid solution and the (N-1)th filtrate in the shaker for the Nth time, centrifuging to obtain bacterial metabolites, and obtaining the Nth filtrate, where N is an integer greater than or equal to 2 and less than or equal to 10.

[0013] The leaching method adopted by the present invention is a step-by-step bioleaching method, which produces biomass sulfuric acid by oxidizing thiothiobacillus, so that the insoluble Li and Mn metals in lithium manganate are converted into soluble metals, thereby completing the leaching process. Compared with the traditional one-step bioleaching process, it has the advantages of high leaching rate and short metal leaching time. Specifically, if a sufficient amount of biomass sulfuric acid solution is added at one time, the reaction causes the concentration of biomass sulfuric acid to be significantly reduced, and the increase in pH value inhibits the biological oxidation activity of oxidizing thiothiobacillus, resulting in a slowdown in the synthesis of subsequent biomass sulfuric acid, and the bioleaching efficiency is low in the second half of the process. By adding in steps, adding a high concentration and then supplementing a low concentration biomass sulfuric acid solution, the pH in the reaction environment can be kept in the acidic range of 2.5 to 3.2, and the activity of oxidizing thiothiobacillus can be guaranteed during the leaching process, ensuring the yield of biomass sulfuric acid during the leaching process. Therefore, when recovering an equal amount of waste positive electrode powder, the step-by-step leaching method has a higher leaching efficiency for lithium and manganese metals than the traditional one-step leaching method, and the time required is shorter.

[0014] As a technical solution of the present invention, the lithium manganate positive electrode sheet comprises a positive electrode active material, a binder and a conductive agent, wherein the chemical formula of the positive electrode active material is LiMn 2-x M x O 4 , wherein M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0≤x≤0.1, the binder includes PVDF, and the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube and graphene.

[0015] As a technical solution of the present invention, the solid-liquid ratio of the positive electrode powder to the first biomass sulfuric acid solution is 50-80 g / L, and the solid-liquid ratio of the positive electrode powder to the second biomass sulfuric acid solution is 30-60 g / L.

[0016] As a technical solution of the present invention, the pre-treatment includes crushing the lithium manganese oxide positive electrode sheets disassembled from the waste batteries to obtain powder with a particle size of 70 to 90 μm, and then using a 100 to 300 mesh sieve coupled with a vibrating agitator to screen to obtain the positive electrode powder.

[0017] As a technical solution of the present invention, the preparation of the initial biomass sulfuric acid comprises: adding 10% by volume of Thiobacillus thiooxidans in a concentration of 4 to 8% to a 9K medium and a sulfur source nutrient; 5 ~10 8 / mL of bacterial stock solution and culture until the density of the Thiobacillus thiooxidans develops to the logarithmic phase of the growth curve and then centrifuge.

[0018] As a technical solution of the present invention, the 9K medium comprises 0.5 g / L of MgSO 4 ·H 2 O, 3.0 g / L of (NH 4 ) 2 SO 4 , 0.5 g / L of K 2 HPO 4 , 0.1 g / L of KCl and 44.22 g / L of FeSO 4 ·H 2 O.

[0019] As a technical solution of the present invention, the sulfur source nutrient is an amino acid containing low-valence sulfur with a concentration of 5 - 20 g / L.

[0020] As a technical solution of the present invention, the pH value of the 9K medium and the sulfur source nutrient is adjusted to 2 - 3 with 98 wt.% sulfuric acid.

[0021] As a technical solution of the present invention, the culture conditions are 25 - 35 °C and the rotation speed is 100 - 200 rpm.

[0022] As a technical solution of the present invention, the shaker maintains a rotation speed of 100 - 200 rpm and a temperature of 25 - 30 °C.

[0023] As a technical solution of the present invention, the first time is 3 - 5 d and the Nth time is 1 - 3 d.

[0024] The second aspect of the present invention provides a method for recovering metals in a lithium manganate-based cathode sheet, comprising:

[0025] (I) Obtaining a leaching solution containing Li + and Mn 2+ and manganese dioxide precipitate according to the aforementioned method for leaching metals in a lithium manganate-based cathode sheet;

[0026] (II) Post-treating the leaching solution to recover Li + and Mn 2+ , and the post-treatment includes at least one operation of precipitation, adsorption, and extraction.

[0027] Using the leaching method of the present invention, a high proportion of Li + and Mn 2+ can be recovered, and the leaching time is short. Specific Embodiments

[0028] The present invention provides a method for leaching and recovering metals in a lithium manganate-based cathode sheet, which can achieve high-proportion leaching and recovery of Li and Mn.

[0029] The lithium manganese oxide-based positive electrode sheet of the present invention refers to a positive electrode sheet containing a lithium manganese oxide-based positive electrode active material. The lithium manganese oxide-based positive electrode sheet includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material includes a lithium manganese oxide-based positive electrode active material, and its chemical formula is LiMn 2-x M x O 4 , where M is at least one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0 ≤ x ≤ 0.1. The binder includes PVDF. The conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube, and graphene. The mass ratio of the positive electrode active material, the binder, and the conductive agent can be, but is not limited to, 85-98:0.5-3.0:0.5-3.0. The positive electrode sheet can be prepared by making a slurry of the positive electrode active material, the binder, and the conductive agent with a solvent, coating it on a positive electrode current collector, drying, rolling, etc.

[0030] The method for leaching metals in the lithium manganese oxide-based positive electrode sheet of the present invention includes the following steps.

[0031] (1) Preparation of materials

[0032] The lithium manganese oxide-based positive electrode sheet disassembled from a waste battery is pretreated to obtain positive electrode powder;

[0033] (2) Biological leaching

[0034] Prepare an initial biomass sulfuric acid containing Thiobacillus thiooxidans, and dilute the initial biomass sulfuric acid to a first biomass sulfuric acid solution and a second biomass sulfuric acid solution with concentrations of 30-50 g / L and 15-25 g / L respectively, and use the first biomass sulfuric acid solution and the second biomass sulfuric acid solution to leach the positive electrode powder.

[0035] Among them, the pretreatment includes crushing the lithium manganese oxide-based positive electrode sheet disassembled from the waste battery to obtain a powder with a particle size of 70-90 μm, and then using a sieve with 100-300 meshes coupled with a vibrating stirrer for screening to obtain positive electrode powder.

[0036] The preparation of the initial biomass sulfuric acid includes: adding a bacterial stock solution with a volume concentration of 4-8% and a number of Thiobacillus thiooxidans of 10 5 ~10 8 / mL to 9K medium and a sulfur source nutrient, and culturing until the density of Thiobacillus thiooxidans develops to the logarithmic phase of the growth curve and then centrifuging. Thiobacillus thiooxidans can use commercially available strains, such as those from Shanghai Bangjing, Ningbo Mingzhou Biology, etc. The life activities of Thiobacillus thiooxidans in the medium can synthesize biomass sulfuric acid from the sulfur source nutrient in the medium, and the expression is S + O 2 + H 2 O → H 2 SO 3, the leaching of Li and Mn metal ions is achieved through the acid action of biomass sulfuric acid. Compared with the strong acids and strong bases used in traditional acid-base methods, biomass sulfuric acid is more environmentally friendly and has the advantages of low cost and simple end-treatment. The 9K medium includes 0.5 g / L of MgSO 4 ·H 2 O, 3.0 g / L of (NH 4 ) 2 SO 4 , 0.5 g / L of K 2 HPO 4 , 0.1 g / L of KCl and 44.22 g / L of FeSO 4 ·H 2 O. The sulfur source nutrient is an amino acid containing low-valent sulfur with a concentration of 5 - 20 g / L, specifically cystine and / or cysteine. The sulfur source nutrient in the medium can promote the leaching process, manifested as 3MnO 2 +S+2H 2 O→SO 4 2- +3Mn 2+ +4OH - . In addition, the content of FeSO 4 ·H 2 O in the medium is relatively high, and its ferrous ion (Fe 2+ ) helps the reduction of MnO 2 , manifested as MnO 2 +2Fe 2+ +4H + →Mn 2+ +2Fe 3+ +2H 2 O. The leaching of Mn can be promoted by reducing MnO 2 to Mn 2+ . The iron reductase produced by Thiobacillus thiooxidans reduces the generated Fe 3+ to Fe 2+ ions, realizing the regeneration of Fe 2+ , thus forming a cyclic mechanism, which can improve the recovery rate of manganese. The pH value of the 9K medium and the sulfur source nutrient is adjusted to 2 - 3 with 98 wt.% sulfuric acid. The cultivation is carried out in a shaker, and the temperature is 25 - 35 °C, and the rotation speed is 100 - 200 rpm. The centrifugation is carried out at a temperature below 4 °C and centrifuged at 8000 - 12000 rpm for 10 - 30 min.

[0037] The concentration of the first biomass sulfuric acid solution is 30 - 50 g / L. As an example, it can be, but is not limited to, 30 g / L, 32 g / L, 34 g / L, 36 g / L, 38 g / L, 40 g / L, 42 g / L, 44 g / L, 46 g / L, 48 g / L, 50 g / L. The concentration of the second biomass sulfuric acid solution is 15 - 25 g / L. As an example, it can be, but is not limited to, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, 21 g / L, 22 g / L, 23 g / L, 24 g / L, 25 g / L. The initial biomass sulfuric acid is diluted with pure water.

[0038] The leaching treatment of the cathode powder with the biomass sulfuric acid solution includes the one - time step S1 and the repeated N - 1 times of step S2. Step S1 includes mixing the first biomass sulfuric acid solution and the cathode powder in a shaker for the first time, then centrifuging to obtain bacterial metabolites and getting the first filtrate. Step S2 includes mixing the second biomass sulfuric acid solution and the (N - 1)th filtrate in a shaker for the Nth time, then centrifuging to obtain bacterial metabolites and getting the Nth filtrate. N is an integer greater than or equal to 2 and less than or equal to 10, which means the leaching treatment includes one - time step S1 and successively 1 - 9 times of step S2. The solid - liquid ratio of the cathode powder and the first biomass sulfuric acid solution is 50 - 80 g / L. As an example, it can be, but is not limited to, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L. The solid - liquid ratio of the cathode powder and the second biomass sulfuric acid solution is 30 - 60 g / L. As an example, it can be, but is not limited to, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L. This solid - liquid ratio is the addition amount of the second biomass sulfuric acid solution each time step S2 is carried out.

[0039] The shaker maintains a rotation speed of 100 - 200 rpm and a temperature of 25 - 30 °C. The first time is 3 - 5 d, preferably 4 d. The Nth time is 1 - 3 d, preferably 2 d. The total number of days for the leaching treatment is 12 - 16 d. During the leaching process, the reaction 2LiMn 2 O 4 +4H + →2Li + +3MnO 2 +Mn 2+ +2H 2 O occurs.

[0040] Using the aforementioned method for leaching metals in the lithium manganate - based cathode sheet can obtain a leaching solution containing Li + and Mn 2+ and manganese dioxide precipitate. The leaching solution is then post - treated to separately recover Li + and Mn 2+The post-treatment includes at least one operation among precipitation, adsorption and extraction. The precipitation can be to precipitate Mn using an alkaline solution (such as sodium hydroxide, potassium hydroxide or ammonia water). 2+ and precipitate Li using a lithium precipitating agent (such as sodium carbonate, potassium carbonate, sodium phosphate or potassium phosphate). + Adsorption is to use different adsorption resins (such as chelating resins containing phosphoric acid groups, phosphorous acid groups, sulfonic acid groups, hypophosphorous acid groups or amino groups; biochars obtained by pyrolyzing peanut shells, reed straws, bamboo shells, buckwheat husks, rice straws or pomelo peels) to treat different metal ions by chelation or adsorption. Extraction is to extract different metal ions using different extractants (such as Mextral 54-100 1-phenyl-1,3-decanedione, P507 2-ethylhexyl phosphoric acid-2-ethylhexyl ester and C272 bis(2,4,4-trimethylpentyl) phosphonic acid).

[0041] To better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the methods described in the following embodiments are further explanatory descriptions of the present invention and should not be regarded as limitations on the present invention.

[0042] Example 1

[0043] This example is a method for leaching metals in a lithium manganese oxide-based cathode sheet, and the steps are as follows.

[0044] (1) Preparation of materials

[0045] Crush the lithium manganese oxide-based cathode sheet (the cathode active material is LiMn 2 O 4 , the binder is PVDF, and the conductive agent is SP, and the mass ratio of the three is 96:2.5:1.5) removed from the used lithium manganese oxide lithium-ion battery to obtain a powder with a particle size of 78±2 μm. Subsequently, screen the obtained powder using a #200 mesh screen coupled with a vibrating stirrer to obtain the cathode powder.

[0046] (2) Biological leaching

[0047] Use 9K medium (0.5 g / L of MgSO 4 ·H 2 O, 3.0 g / L of (NH 4 ) 2 SO 4 , 0.5 g / L of K 2 HPO 4 , 0.1 g / L of KCl and 44.22 g / L of FeSO 4 ·H 2(O) and a sulfur source nutrient (cystine) with a concentration of 15 g / L, and the pH was adjusted to 2 - 3 with 98 wt.% sulfuric acid. Thiobacillus thiooxidans bacteria were added to the culture medium at a volume concentration of 6%, and the number of bacteria in the stock solution was 10 7 / mL. The biological culture was carried out in a shaker at 28°C with a rotation speed of 180 rpm. When the density of Thiobacillus thiooxidans developed to the logarithmic phase of the growth curve, the culture medium was centrifuged at 10000 rpm for 20 min at 4°C to obtain the initial biomass sulfuric acid.

[0048] Part of the initial biomass sulfuric acid was diluted with pure water to a first biomass sulfuric acid solution with a concentration of 45 g / L, and another part was diluted with pure water to a second biomass sulfuric acid solution with a concentration of 23 g / L. The positive electrode powder and the first biomass sulfuric acid solution (the solid-liquid ratio of the positive electrode powder and the first biomass sulfuric acid solution was 65 g / L) were mixed in a shaker. The rotation speed of the shaker was 150 rpm and the temperature was 28°C. On the 4th day of mixing, it was centrifuged at 10000 rpm for 15 min at 4°C to separate the bacterial metabolites from the residue to obtain the first filtrate. The first filtrate and the second biomass sulfuric acid solution (the solid-liquid ratio of the positive electrode powder and the second biomass sulfuric acid solution was 35 g / L) were mixed in a shaker. The rotation speed of the shaker was 130 rpm and the temperature was 28°C. After mixing for 2 d (i.e., on the 6th day of leaching), it was centrifuged at 10000 rpm for 15 min at 4°C to separate the bacterial metabolites from the residue to obtain the second filtrate. On the 8th day, 10th day, and 12th day of leaching, the filtrate and the second biomass sulfuric acid solution (the solid-liquid ratio of the positive electrode powder and the second biomass sulfuric acid solution was 35 g / L) were mixed in a shaker. The rotation speed of the shaker was 130 rpm and the temperature was 28°C. After mixing for 2 d, it was centrifuged at 10000 rpm for 15 min at 4°C to separate the bacterial metabolites from the residue to obtain the filtrate.

[0049] Example 2

[0050] This example is a method for leaching metals in a lithium manganate-based positive electrode sheet, and the steps are as follows.

[0051] (1) Preparation of materials

[0052] The lithium manganate-based positive electrode sheet (the positive electrode active material is LiMn 2 O 4 , the binder is PVDF, and the conductive agent is SP, and the mass ratio of the three is 96:2.5:1.5) removed from the used lithium manganate lithium-ion battery was crushed to obtain powder with a particle size of 85 ± 2 μm. Subsequently, the obtained powder was screened using a #200 mesh sieve coupled with a vibrating stirrer to obtain the positive electrode powder.

[0053] (2) Biological leaching

[0054] Using 9K medium (0.5 g / L of MgSO 4 ·H 2 O, 3.0 g / L of (NH 4 ) 2 SO 4 , 0.5 g / L of K 2 HPO 4 , 0.1 g / L of KCl and 44.22 g / L of FeSO 4 ·H 2 O) and a sulfur source nutrient (cysteine) with a concentration of 13 g / L, adjusting the pH to 2 - 3 with 98 wt.% sulfuric acid. Adding Thiobacillus thiooxidans bacterial stock solution with a bacterial count of 10 6 / mL to the medium at a volume concentration of 5%. Conducting bioculture in a shaker at 30 °C with a rotation speed of 150 rpm until the density of Thiobacillus thiooxidans develops to the logarithmic phase of the growth curve, and then centrifuging the culture medium at 4 °C at 8000 rpm for 30 min to obtain the initial biomass sulfuric acid.

[0055] Taking a part of the initial biomass sulfuric acid and diluting it with pure water to a first biomass sulfuric acid solution with a concentration of 40 g / L, and taking another part and diluting it with pure water to a second biomass sulfuric acid solution with a concentration of 20 g / L. Mixing the positive electrode powder material and the first biomass sulfuric acid solution (the solid - liquid ratio of the positive electrode powder material and the first biomass sulfuric acid solution is 76 g / L) in a shaker, with the rotation speed of the shaker being 180 rpm and the temperature being 30 °C. On the 4th day of mixing, centrifuging at 4 °C at 8500 rpm for 10 min to separate the bacterial metabolites from the residue to obtain the first filtrate. Mixing the first filtrate and the second biomass sulfuric acid solution (the mass ratio of the positive electrode powder material and the second biomass sulfuric acid solution is a solid - liquid ratio of 50 g / L) in a shaker, with the rotation speed of the shaker being 130 rpm and the temperature being 28 °C. After mixing for 2 d (i.e., on the 6th day of leaching), centrifuging at 4 °C at 10000 rpm for 15 min to separate the bacterial metabolites from the residue to obtain the second filtrate. On the 8th day, 10th day, 12th day, and 14th day of leaching, mixing the filtrate and the second biomass sulfuric acid solution (the mass ratio of the positive electrode powder material and the second biomass sulfuric acid solution is a solid - liquid ratio of 50 g / L) in a shaker, with the rotation speed of the shaker being 140 rpm and the temperature being 30 °C. After mixing for 2 d, centrifuging at 4 °C at 9000 rpm for 12 min to separate the bacterial metabolites from the residue to obtain the filtrate.

[0056] Comparative Example 1

[0057] This comparative example is a method for leaching metals in a lithium manganate - based positive electrode sheet, and its steps are as follows.

[0058] (1) Preparation of materials

[0059] The lithium manganese oxide-based positive electrode sheet (the positive electrode active material is LiMn 2 O 2 , the binder is PVDF, and the conductive agent is SP, and the mass ratio of the three is 96:2.5:1.5) removed from the waste lithium manganese oxide lithium-ion battery is crushed to obtain a powder with a particle size of 78 ± 2 μm. Subsequently, the obtained powder is screened using a #200 mesh sieve and a vibration stirrer coupled to obtain the positive electrode powder.

[0060] (2) Biological leaching

[0061] Using 9K medium (0.5 g / L of MgSO 4 ·H 2 O, 3.0 g / L of (NH 4 ) 2 SO 4 , 0.5 g / L of K 2 HPO 4 , 0.1 g / L of KCl and 44.22 g / L of FeSO 4 ·H 2 O) and a sulfur source nutrient (cystine) with a concentration of 15 g / L, and the pH is adjusted to 2 - 3 with 98 wt.% sulfuric acid. Add the bacteria stock solution of Thiobacillus thiooxidans with a bacterial count of 10 7 / mL to the medium at a volume concentration of 6%. Biologically culture in a shaker at 28°C at a rotation speed of 180 rpm until the density of Thiobacillus thiooxidans develops to the logarithmic stage of the growth curve, and then centrifuge the culture medium at 4°C at 10000 rpm for 20 min to obtain the initial biomass sulfuric acid.

[0062] Dilute the initial biomass sulfuric acid with pure water to a biomass sulfuric acid solution with a concentration of 55 g / L. Mix the positive electrode powder and the biomass sulfuric acid solution (the solid-liquid ratio of the positive electrode powder and the biomass sulfuric acid solution is 50 g / L) in a shaker. The rotation speed of the shaker is 150 rpm and the temperature is 28°C. On the 18th day of mixing, centrifuge at 4°C at a rotation speed of 10000 rpm for 15 min to separate the bacterial metabolites from the residue to obtain the filtrate.

[0063] Calculate the leaching rates of various metal ions in the leaching solutions of Examples 1 - 2 and Comparative Example 1 on the 6th day, 8th day, 10th day, 12th day of leaching and after the leaching is completed. The results are shown in Table 1. Ion recovery is carried out on the leaching solutions finally obtained in Examples 1 - 2 and Comparative Example 1. The recovery method is as follows, and the recovery rates of various metal ions are shown in Table 1.

[0064] Recovery method: Add the leaching solution to a 10.0 wt.% sodium hydroxide solution to precipitate and recover manganese, and then add a saturated sodium carbonate solution to the filtrate at 50°C and react for 2 h to crystallize out lithium carbonate.

[0065] Table 1 Metal Leaching Rates and Recovery Rates of Examples 1-2 and Comparative Example 1

[0066]

[0067]

[0068] As can be seen from the results in Table 1, the leaching methods of Examples 1-2 use a stepwise bioleaching method, in which Thiobacillus thiooxidans produces biomass sulfuric acid, converting the insoluble Li and Mn metals in lithium manganate into soluble metals. The leaching rate and recovery rate are high, and the leaching time is short. In Comparative Example 1, a one-step bioleaching method is used, and the change in the leaching rate is not obvious in the later stage of leaching. This is because a sufficient amount of biomass sulfuric acid solution is added in the initial stage, and the reaction causes a significant decrease in the concentration of biomass sulfuric acid, and the increase in pH value inhibits the biological oxidation activity of Thiobacillus thiooxidans, resulting in a slowdown in the synthesis of subsequent biomass sulfuric acid.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and do not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to only those listed in the embodiments. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for leaching metal from a lithium manganese oxide positive electrode sheet, characterized in that: include: (1) Preparation The lithium manganese oxide positive electrode sheets disassembled from waste batteries are pre-treated to obtain positive electrode powder; (2) Bioleaching Initial biomass sulfuric acid containing Thiobacillus thiooxidans is prepared, and the initial biomass sulfuric acid is diluted to a first biomass sulfuric acid solution and a second biomass sulfuric acid solution with concentrations of 30-50 g / L and 15-25 g / L, respectively. The first biomass sulfuric acid solution and the second biomass sulfuric acid solution are used to leaching the cathode powder. The leaching treatment includes a step S1 once and a step S2 repeated N-1 times. Step S1 includes mixing the first biomass sulfuric acid solution and the cathode powder in a shaking table for a first time, then centrifuging out bacterial metabolites to obtain a first filtrate, and step S2 includes mixing the second biomass sulfuric acid solution and the N-1th filtrate in the shaking table for an Nth time, then centrifuging out bacterial metabolites to obtain an Nth filtrate, where N is an integer greater than or equal to 2 and less than or equal to 10.

2. The method for leaching metal from a lithium manganate positive electrode sheet according to claim 1, characterized in that: The solid-liquid ratio of the positive electrode powder to the first biomass sulfuric acid solution is 50-80 g / L, and the solid-liquid ratio of the positive electrode powder to the second biomass sulfuric acid solution is 30-60 g / L.

3. The method for leaching metal from a lithium manganese oxide positive electrode sheet according to claim 1, characterized in that: The pre-treatment includes crushing the lithium manganese oxide positive electrode sheet disassembled from the waste battery to obtain a powder with a particle size of 70 to 90 μm, and then screening using a 100 to 300 mesh sieve coupled with a vibrating agitator to obtain the positive electrode powder.

4. The method for leaching metal from a lithium manganate positive electrode sheet according to claim 1, characterized in that: The preparation of the initial biomass sulfuric acid comprises: adding 10% sulfur oxidizing bacillus at a volume concentration of 4-8% to a 9K medium and a sulfur source nutrient; 5 ~10 8 / mL of bacterial stock solution and culture until the density of the Thiobacillus thiooxidans develops to the logarithmic phase of the growth curve and then centrifuge.

5. The method for leaching metal from a lithium manganese oxide positive electrode sheet according to claim 4, characterized in that: The 9K culture medium includes 0.5 g / L of MgSO4·H2O, 3.0 g / L of (NH4)2SO4, 0.5 g / L of K2HPO4, 0.1 g / L of KCl and 44.22 g / L of FeSO4·H2O.

6. The method for leaching metal from a lithium manganese oxide positive electrode sheet according to claim 4, characterized in that: The sulfur source nutrient is an amino acid containing low-valent sulfur at a concentration of 5 to 20 g / L.

7. The method for leaching metal from a lithium manganese oxide positive electrode sheet according to claim 4, characterized in that: The pH value of the 9K culture medium and the sulfur source nutrient is adjusted to 2-3 by using 98 wt.% sulfuric acid.

8. The method for leaching metal from a lithium manganate positive electrode sheet according to claim 4, characterized in that: The culture conditions are 25-35° C. and the rotation speed is 100-200 rpm.

9. The method for leaching metal from a lithium manganate positive electrode sheet according to claim 1, characterized in that: The shaking table maintains a rotation speed of 100-200 rpm and a temperature of 25-30°C.

10. A method for recovering metals from lithium manganate positive electrode sheets, characterized in that: include: (I) The method for leaching metal from a lithium manganate positive electrode sheet according to any one of claims 1 to 9 to obtain a Li-containing + and Mn 2+ The leachate and manganese dioxide precipitation; (II) Post-treatment of the leachate to recover Li + and Mn 2+ , the post-treatment includes at least one operation of precipitation, adsorption and extraction.

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