Method for reducing carbon by coupling water extraction of lithium from reduced black powder and flotation of negative electrode material

Abstract

The invention discloses a method for reducing carbon by coupling reduced black powder lithium water leaching and negative electrode material flotation, and belongs to the technical field of battery recovery. After the waste lithium ion battery electrode material mixture black powder is subjected to heat treatment, water is added, stirring is performed to generate black powder ore pulp, then a graphite flotation reagent is added, sealed flotation is performed, meanwhile, micro-nano bubble water containing carbon dioxide gas is filled, lithium ions are selectively leached into deionized water in the flotation process, and a negative electrode material becomes concentrate foam; the positive electrode material enters tailings; according to the method, selective lithium extraction is carried out in the process of sorting the positive electrode material and the negative electrode material, recycling of the negative electrode material is facilitated, the leaching efficiency of the positive electrode material is improved, the chemical lithium extraction process is simplified, the technological process is shortened, and leaching residues are greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field related to the recycling of waste batteries, and particularly relates to a method for coupling carbon reduction of lithium extraction from reduced black powder by water leaching and flotation of anode materials. Background Art

[0002] At present, insufficient attention is paid to the recycling of graphite, the anode material of lithium batteries. When entering the leaching process, graphite residues are generated, which are likely to cause environmental pollution and make it difficult to recycle the anode graphite. In the traditional waste lithium-ion battery treatment process, reduced black powder is subjected to water leaching for lithium extraction, and the remaining lithium extraction residues are further treated by acid leaching to recover valuable elements such as nickel, cobalt, and manganese in the cathode material. The remaining graphite residues after leaching are difficult to handle and recycle. When flotation separation of electrode materials is carried out, insufficient consideration is given to the leaching of lithium elements, and the flotation anode materials contain lithium elements, resulting in lithium element loss.

[0003] The prior art with the publication number CN113206227A proposes a simple and efficient regeneration process, enabling the simultaneous recycling and regeneration of waste nickel-cobalt-manganese cathode and graphite anode materials into anode materials for sodium-ion batteries, belonging to the technical field of lithium-ion battery material recycling. It mainly includes the following steps: Step 1, mixing waste cathode and anode powders with sublimed sulfur in a certain proportion and carrying out mechanical ball milling to achieve uniform compounding; Step 2, performing high-temperature calcination in a tube furnace to prepare a carbon-based metal sulfide composite material in one step; Step 3, subjecting the composite material to water leaching for lithium extraction. After the leaching residue is dried, it can be directly used as the anode material for sodium-ion batteries. However, it has problems such as low reduction efficiency, excessive use of reagents, and multiple reduction steps, and cannot achieve an efficient separation effect. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a method for coupling carbon reduction of lithium extraction from reduced black powder by water leaching and flotation of anode materials, which simultaneously realizes the leaching of lithium elements during the flotation separation of anode materials, and uses carbon dioxide micro-nano bubble water for flotation and lithium extraction. It can not only consume carbon dioxide while effectively improving the flotation efficiency, but also simultaneously convert lithium elements into soluble lithium bicarbonate during the flotation process, reducing the steps of using different reagents for lithium extraction multiple times, that is, improving the lithium element leaching efficiency and reducing the dosage of reagents, being highly efficient and environmentally friendly.

[0005] To achieve the above technical objectives, the present invention discloses a method for coupling carbon reduction of lithium extraction from reduced black powder by water leaching and flotation of anode materials, which is characterized in that the steps are as follows:

[0006] Crush and roast waste lithium-ion batteries to obtain black powder, which is a mixture of positive and negative electrode materials.

[0007] Mix the black powder with deionized water at a ratio of 30 - 60 g / L, and then add a flotation reagent for the anode material and stir strongly to form a black powder pulp.

[0008] Feed the black powder pulp into a flotation device in a sealed environment for flotation. During the flotation process, inject micro-nano bubble water mixed with carbon dioxide into the sealed environment, and use the bubble water to supplement water for the flotation process. Utilize the fact that micro-nano bubbles can increase the gas-liquid interface, enhance the contact rate between bubbles and mineral particles, and improve the flotation effect. Part of the carbon dioxide dissolves in the water, making the water weakly acidic. At the same time, the micro-nano bubbles are also adsorbed on the black powder particles, effectively improving the flotation effect. Based on water leaching of lithium, carbon dioxide is consumed, and it reacts with insoluble lithium carbonate to form lithium bicarbonate.

[0009] The anode material in the black powder pulp is discharged through the concentrate foam of flotation, and the cathode material is discharged through the tailings of flotation. Filter the concentrate foam and tailings separately, collect the filtrate for lithium precipitation, and evaporate and crystallize to obtain lithium carbonate products.

[0010] The filtered anode material is further repaired and regenerated. The cathode material obtained after filtration is used as a product or subjected to acid leaching to extract metal materials such as nickel, cobalt, and manganese therein.

[0011] Furthermore, seal the flotation device to prevent carbon dioxide leakage during operation; the concentrate outlet of the flotation device outputs graphite as the battery anode material; filter and recycle the tailings outlet of the flotation device to obtain the battery cathode material, and perform acid leaching on the filtered solid matter to recover transition metal elements; collect all the filtrates during the flotation process and evaporate and crystallize to obtain lithium carbonate products, realizing the synchronous implementation of the reduction of black powder water leaching of lithium and the flotation separation process of electrode materials.

[0012] Furthermore, the gas charging amount of carbon dioxide gas in the micro-nano bubble water ranges from 0.6 - 1.4 L / min. The micro-nano bubbles improve the flotation efficiency of the battery fine particles and effectively enhance the solubility of carbon dioxide in the aqueous solution, thus creating more favorable conditions for lithium element leaching; in addition, the addition of carbon dioxide not only improves the leaching efficiency of lithium element in the electrode material, but also further improves the flotation separation effect of the positive and negative electrode materials due to the enhanced acidity of the solution without using acidic substances.

[0013] Furthermore, the dosage of the flotation reagent added to the black powder and deionized water is 50 - 300 g / t; the flotation reagent includes: n-dodecane, kerosene, diesel, fatty acid, and the foaming agent is selected from one or a mixture of sec-octanol, terpineol, and methyl isobutyl carbinol.

[0014] Furthermore, for the concentrate foam of the flotation anode material, the remaining gas released after defoaming is recycled and returned to the flotation aeration.

[0015] Further, carbon dioxide gas is collected through the pyrolysis process of waste lithium-ion batteries or other carbon dioxide emission links as the gas source of carbon dioxide micro-nano bubble water used for flotation.

[0016] Beneficial effects: In this method, the black powder of the electrode material formed after the reduction roasting of waste lithium-ion batteries realizes the leaching of lithium elements in water during the process of flotation separation of the positive and negative electrode materials. Only one step is required to fully separate the positive and negative electrode materials, without the need for multiple element separations, effectively improving the sorting efficiency. This method simultaneously realizes the selective lithium extraction from the black powder after the pyrolysis treatment of waste lithium-ion batteries and the flotation separation of the negative electrode material, which is beneficial to the reuse of the negative electrode material and improves the leaching efficiency of the subsequent positive electrode material, significantly reducing the generation of leaching residues. This method can preferentially separate the negative electrode material, shorten the process flow, and has broad application prospects. Description of the Drawings

[0017] Figure 1 is a schematic flow chart of the method for coupling lithium extraction from reduced black powder by water leaching and flotation of negative electrode material with carbon reduction of the present invention;

[0018] Figure 2 is a schematic diagram of the graphite separation rate by micro-nano bubble flotation in the embodiment of the present invention;

[0019] Figure 3 is a schematic diagram of the influence law of the solid-liquid ratio on the lithium leaching rate in the embodiment of the present invention;

[0020] Figure 4 is a diagram showing the influence of the aeration time and flow rate of micro-nano CO2 bubble water on the flotation effect in Example 4 of the present invention;

[0021] Figure 5 is a scanning electron microscope (SEM) picture in Example 5 of the present invention, where a) is the reduced ternary positive electrode; b) is the pyrolyzed negative electrode; c) is carbon. Specific Embodiment Method

[0023] The following further describes the embodiments of the present invention with reference to the drawings.

[0024] As Figure 1 shown, the present invention discloses a method for coupling lithium extraction from reduced black powder by water leaching and flotation of negative electrode material with carbon reduction, and the steps are as follows:

[0025] The black powder obtained after heat treatment of waste lithium-ion batteries and deionized water enter the stirring and pulp-adjusting equipment according to a certain ratio for strong stirring. Meanwhile, flotation reagents for graphite are added, and the black powder pulp enters the flotation equipment for flotation. During flotation, micro-nano bubble water containing carbon dioxide gas is introduced. During the flotation process, lithium ions are selectively leached into the deionized water, the negative electrode material becomes concentrated ore foam, and the positive electrode material enters the tailings. The foam of the negative electrode material separated by flotation is defoamed, and the remaining gas is recycled back to the flotation aeration. The negative electrode material and the positive electrode material are filtered separately, and the filtrates are mixed together for lithium precipitation and evaporation crystallization to obtain lithium carbonate products, and the evaporated liquid is returned to the stirring tank for recycling. The filtered negative electrode material is further repaired and recycled, and the positive electrode material obtained after filtration can be used as a product or subjected to acid leaching to extract metal materials such as nickel, cobalt, and manganese therein. This process simultaneously realizes the selective lithium extraction from the black powder after pyrolysis treatment of waste lithium-ion batteries and the flotation separation of the negative electrode material, which is beneficial to the reuse of the negative electrode material, improves the leaching efficiency of the subsequent positive electrode material, and significantly reduces the generation of leaching residues. This process improves the extraction efficiency of lithium in waste lithium-ion batteries, preferentially separates the negative electrode material, shortens the process flow, and has broad application prospects.

[0026] Example 1:

[0027] Micro-nano carbon dioxide bubble water is prepared by a micro-nano bubble generating device with the product model XZCP-K. The reduced-roasted black powder of waste ternary lithium-ion batteries and the micro-nano carbon dioxide bubble water enter the stirring and pulp-adjusting equipment at a ratio of 40 g / L for strong stirring, and kerosene with a flotation reagent dosage of 200 g / t and methyl isobutyl carbinol with a dosage of 150 g / t are added; then the black powder pulp enters the flotation device XFD-0.5L for flotation. During flotation, micro-nano bubble water containing carbon dioxide is introduced. The gas charging amount range of carbon dioxide when preparing the micro-nano carbon dioxide bubble water is 1.0 L / min. The insoluble lithium-containing substances in the reduced-roasted black powder react with carbon dioxide to form soluble lithium bicarbonate. During the flotation process, the negative electrode graphite is separated as concentrated ore, and nickel-cobalt-manganese compounds are used as tailings. The lithium element in the ternary positive electrode material dissolves in the deionized water, and lithium ions are enriched by evaporation crystallization to obtain lithium carbonate precipitation.

[0028] Example 2:

[0029] Micro-nano CO2 bubble water is prepared by a micro-nano bubble generating device with the product model XZCP-K. The reduced-roasted black powder of the positive electrode of waste ternary lithium-ion batteries and the pyrolyzed waste negative electrode are mixed at a mass ratio of 3:1. The mixed black powder and the micro-nano carbon dioxide bubble water enter the flotation cell at a ratio of 40 g / L, and kerosene with a flotation reagent dosage of 200 g / t and methyl isobutyl carbinol with a dosage of 150 g / t are added to carry out the flotation rate experiment. The flotation results are as Figure 1As shown, as time increases, the grade of graphite decreases, while the recovery rate of graphite increases significantly. As time continues to increase, the rate of increase in the recovery rate slows down, and the rate of decrease in the grade becomes larger. According to Figure 2 the rate of graphite separation by micro-nano bubble flotation shown, considering the flotation time comprehensively, 6 minutes is selected.

[0030] Example 3:

[0031] First, the ternary lithium-ion battery after reduction roasting is digested, and after dilution, the element content it contains is tested. The element content is shown in Table 1. Under normal temperature environment, under the leaching condition with a leaching time of 20 min, the influence of different solid-liquid ratios on the leaching rate of lithium element in the process of water leaching and micro-nano CO2 bubble leaching of the reduced-roasted ternary lithium-ion battery is explored. The calculation formula for the leaching rate of lithium element is shown in Formula 1; through Figure 3 the influence law of the solid-liquid ratio on the lithium leaching rate shown, the results show that the introduction of micro-nano CO2 bubbles significantly improves the leaching efficiency of lithium.

[0032] Table 1 Element content (mg / g) tested by ICP

[0033]

[0034]

[0035] In the formula

[0036] c i represents the concentration of lithium element in the filtrate;

[0037] V i represents the volume of the filtrate;

[0038] m i represents the mass of the leached ternary cathode;

[0039] ω represents the lithium element content contained in each gram of the ternary cathode.

[0040] Example 4:

[0041] Based on the flotation results of 300 g / t kerosene and 150 g / t MIBC, the influence of the preparation time of 2 - 10 min and the preparation flow rate of 400 - 800 mL / min on the flotation effect is investigated. The experimental results reveal that the introduction of CO2 can significantly improve the flotation performance. Compared with the benchmark flotation results, both the grade and the recovery rate are increased by about 2%. This phenomenon may be attributed to the decrease in the pH value of the solution caused by the addition of CO2, thus enhancing the flotation effect in an acidic environment. Among them, the influence of the aeration time and flow rate of micro-nano CO2 bubbles on the flotation effect is as Figure 4 shown, Figure 4a) and b) in it represent the graphs of the grade and recovery rate of flotation recovery of graphite at different aeration times, and c) and d) are the grade and recovery rate of flotation recovery of graphite at different aeration flows. The blue curve represents the effect of micro-nano bubble flotation without adding carbon dioxide. Through comparative experiments, it is shown that the addition of CO2 bubbles will enhance the flotation recovery effect. In addition, it can also show the influence law of time and flow rate in the preparation process of micro-nano CO2 bubble water on the flotation recovery effect.

[0042] Example 5:

[0043] Select the ternary cathode material after reduction roasting, the pyrolyzed graphite, and the coal after vibration milling, and use a scanning electron microscope to analyze the differences on the surfaces of the electrode material and the coal material, such as Figure 5 shown. It is observed that the particle size of the ternary positive and negative electrode materials is about 20 microns, while the particle size of the milled coal is about 150 microns. Relatively speaking, the electrode material belongs to fine-grained particles compared with coal. Micro-nano bubbles can significantly improve the recovery rate of ultrafine particles, preferentially adsorb on the surface of hydrophobic particles, make fine particles aggregate into larger particles, enhance the collision probability between bubbles and particles, and thus strengthen the flotation effect. Verified by the scanning results, micro-nano bubbles are indeed suitable for fine-grained particles such as electrode materials, providing a way to enhance the flotation separation effect between positive and negative electrodes.

[0044] The above are only individual embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for reducing carbon by leaching lithium from reduced black powder and coupling flotation of negative electrode materials, characterized in that: Here are the steps: The waste lithium-ion batteries are crushed and roasted to obtain black powder, which is a mixture of positive and negative electrode materials. Mix the black powder with deionized water at a ratio of 30-60g / L, then add the flotation reagent of the negative electrode material and stir vigorously to form a black powder slurry; The black powder slurry is fed into a flotation device in a sealed environment for flotation, and micro-nano bubble water mixed with carbon dioxide is introduced into the sealed environment during the flotation process, and the bubble water is used to supplement water for the flotation process; and the micro-nano bubbles can increase the gas-liquid interface, increase the contact rate between bubbles and mineral particles, and improve the flotation effect. Part of the carbon dioxide is dissolved in the water to make the water weakly acidic. At the same time, the micro-nano bubbles are also adsorbed on the black powder particles to effectively improve the flotation effect, consume carbon dioxide on the basis of water leaching lithium, and generate lithium bicarbonate with insoluble lithium carbonate; The negative electrode material in the black powder slurry is discharged through the flotation concentrate foam, and the positive electrode material is discharged through the flotation tailings. The concentrate foam and tailings are filtered separately, and the filtrate is collected for lithium precipitation, evaporation and crystallization to obtain lithium carbonate products; The filtered negative electrode material is further repaired and regenerated, and the positive electrode material obtained after filtration is used as a product, or acid-leached to extract metal materials such as nickel, cobalt, and manganese.

2. The method for reducing carbon by leaching lithium from reduced black powder and coupling flotation of negative electrode materials according to claim 1, characterized in that: The flotation device is sealed to prevent leakage of carbon dioxide during operation; the concentrate outlet of the flotation device outputs graphite as the negative electrode material of the battery; the tailings outlet of the flotation device is filtered and recovered to obtain the positive electrode material of the battery, and the filtered solid matter is acid-leached to recover the transition metal elements; all the filtrate in the flotation process is collected and evaporated and crystallized to obtain lithium carbonate products, thereby realizing the simultaneous implementation of the black powder water leaching lithium extraction and electrode material flotation separation process.

3. The method for reducing carbon by leaching lithium from reduced black powder in water and coupling flotation of negative electrode materials according to claim 1, characterized in that: The inflation volume of carbon dioxide gas in micro-nano bubble water ranges from 0.6-1.4L / min. Micro-nano bubbles improve the flotation efficiency of battery fine particles and effectively enhance the solubility of carbon dioxide in aqueous solution, thereby creating more favorable conditions for lithium leaching. In addition, the addition of carbon dioxide not only improves the leaching efficiency of lithium in electrode materials, but also further improves the flotation separation effect of positive and negative electrode materials without using acidic substances due to the enhanced acidity of the solution.

4. The method for reducing carbon by leaching lithium from reduced black powder in water and coupling flotation of negative electrode materials according to claim 1, characterized in that: The amount of flotation reagent added to the black powder and deionized water is 50-300g / t; the flotation reagent includes: n-dodecane, kerosene, diesel, fatty acid, and the foaming agent is selected from one or a mixture of sec-octanol, pine alcohol, and methyl isobutyl carbinol.

5. The method for reducing carbon by leaching lithium from reduced black powder and coupling flotation of negative electrode materials according to claim 1, characterized in that: The residual gas released from the concentrated foam of the negative electrode material after defoaming is circulated back to the flotation aeration.

6. The method for reducing carbon by leaching lithium from reduced black powder and coupling flotation of negative electrode materials according to claim 1, characterized in that: Carbon dioxide gas is collected through the pyrolysis process of waste lithium-ion batteries or other carbon dioxide emission links as the gas source for carbon dioxide micro-nano bubble water used for flotation.

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