Flotation separation reagent for positive and negative electrode materials of waste batteries, inhibitor and preparation method and application thereof

Abstract

The application belongs to the technical field of retired power battery recycling, and particularly relates to a waste battery positive and negative electrode material flotation separation reagent, an inhibitor, a preparation method and application thereof. The flotation separation reagent is named PDA, and a structural formula thereof is shown as formula I. The application further provides a preparation method for preparing a flotation inhibitor PDA-SP containing PDA. The patent provides a novel small-molecule organic inhibitor PDA through a chemical synthesis method. The inhibitor has a short molecular chain, can change the wettability difference of the waste battery positive and negative electrode material surface through selective adsorption, thereby improving the flotation separation efficiency of the waste battery positive and negative electrode material, and has important significance for developing a more efficient and environmentally-friendly battery recycling process.

Description

Technical Field

[0001] This invention belongs to the field of retired power battery recycling technology, specifically relating to a flotation separation agent for positive and negative electrode materials of waste batteries, a flotation separation inhibitor, its preparation method and application. Background Technology

[0002] The recycling of retired batteries is an important issue for environmental protection and resource regeneration. The efficient separation of graphite cathode and ternary lithium / lithium cobalt oxide anode materials is of great significance for realizing the reuse of spent batteries.

[0003] Flotation, as an effective physical separation technique, achieves selective separation of different materials by controlling the surface chemical properties of minerals. The positive electrode materials of waste lithium-ion batteries are mainly ternary lithium / lithium cobalt oxide / lithium iron phosphate, while the negative electrode material is usually graphite. Graphite is a non-polar mineral with good hydrophobicity, while ternary lithium / lithium cobalt oxide / lithium iron phosphate, as ionic crystals, are highly hydrophilic. From a flotation theory perspective, separating positive and negative electrode materials using flotation based on the difference in surface hydrophilicity and hydrophobicity is feasible. However, the presence of polyvinylidene fluoride (PVDF) as a binder on the surface of the positive electrode material makes it extremely hydrophobic, leading to difficulties in separating the positive and negative electrode materials and resulting in low recovery rates and grades.

[0004] Therefore, research on novel flotation depressants plays a crucial role in this process. Their mechanism of action primarily involves selective adsorption, altering the surface wettability differences of materials, thereby improving flotation separation efficiency and selectivity. Current research often uses organic depressants, such as carboxymethyl cellulose, gum arabic, and starch. However, these organic depressants, due to their long carbon chains, are prone to particle aggregation, resulting in a high concentration of gangue minerals and low grades of the target mineral. Furthermore, these organic depressants exhibit poor adsorption selectivity and low recovery rates of key materials.

[0005] Therefore, providing a novel flotation inhibitor that can effectively improve the flotation separation efficiency of positive and negative electrode materials of retired power batteries is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, one objective of this invention is to provide a flotation separation agent for the positive and negative electrode materials of waste batteries.

[0007] The technical solution adopted in this invention is as follows:

[0008] A flotation separation agent for positive and negative electrode materials of waste batteries, wherein the flotation separation inhibitor is named PDA, and its structural formula is shown in Formula I:

[0009]

[0010] The second objective of this invention is to provide a flotation separation inhibitor for the positive and negative electrode materials of waste batteries, wherein the flotation separation inhibitor comprises the reagent PDA as described in claim 1.

[0011] The third objective of this invention is to provide a method for preparing the flotation separation inhibitor for the positive and negative electrode materials of waste batteries as described above, comprising the following steps:

[0012] S1. Prepare an aqueous solution of sodium acetate, and adjust the pH of the sodium acetate aqueous solution to 4.5-5.5 using hydrochloric acid or sodium hydroxide;

[0013] S2. Add the set amount of dopamine hydrochloride to the sodium acetate aqueous solution, stir to dissolve, and obtain mixed solution A;

[0014] S3. Add the set amount of sodium periodate to mixed solution A, stir to dissolve, and obtain mixed solution B;

[0015] S4. The mixed solution B is placed at room temperature to obtain a flotation separation inhibitor containing the reagent PDA, which is named PDA-SP.

[0016] Preferably, the concentration of the sodium acetate aqueous solution is 50–100 mM.

[0017] Preferably, the amount of dopamine hydrochloride used is 1-4 mg / mL, and the mixture is stirred for 30 min at a stirring speed of 150 rpm.

[0018] Preferably, the amount of sodium periodate used is 2-8 mg / mL, the reaction is stirred for 1-4 hours, and the stirring speed is 150 rpm.

[0019] Preferably, in steps S1-S4, the system temperature is 20-40℃.

[0020] The fourth objective of this invention is to provide an application of the flotation separation inhibitor prepared by the above method in the flotation recycling of positive and negative electrode materials of waste lithium-ion batteries, comprising the following steps:

[0021] S1. Waste lithium-ion battery positive and negative electrode materials are mixed, crushed, and finely ground until the mass percentage of particles with a size of less than 200 mesh in the material is ≥85%;

[0022] S2. After being soaked in ethanol, the finely ground material is separated, fed into a flotation cell, and water is added to adjust the slurry to obtain flotation slurry;

[0023] S3. Add the flotation separation inhibitor PDA-SP at a concentration of 0.05 mg / L, rotate at 1500 rpm, and adjust the slurry for 3 minutes.

[0024] S4. Continue stirring, add the collector and foaming agent in sequence, and stir to adjust the slurry for the set time;

[0025] S5. Aeration flotation, collecting flotation foam to obtain negative electrode material; collecting flotation tailings, i.e., positive electrode material.

[0026] Preferably, in step S2, the finely ground material is immersed in an ethanol solution, stirred at 150 rpm for 5 minutes to separate the solid and liquid, and then put into a flotation cell. Water is added at a ratio of 1g:50ml to adjust the slurry, and the stirring speed is 1500 rpm for 1 minute to obtain the flotation slurry.

[0027] Preferably, in step S4, the collector is kerosene, added at a rate of 80 mg / L, with slurry preparation for 5 min and rotation speed of 1500 rpm; the foaming agent is methyl isobutyl methanol (MIBC), added at a rate of 3 mg / L, with slurry preparation for 1 min and rotation speed of 1500 rpm.

[0028] The beneficial effects of this invention are as follows:

[0029] This patent achieves the development of a small-molecule organic inhibitor through chemical synthesis. This inhibitor has a short molecular chain and strong selectivity, effectively improving the flotation separation efficiency of positive and negative electrode materials in retired power batteries. Firstly, PDA-SP is used as a selective flotation inhibitor to separate lithium-containing active materials / PVDF and negative electrode material graphite from waste lithium-ion batteries. Its adsorption mechanism is mainly due to the strong cationic attraction between metal ions and hydroxyl functional groups in the PDA-SP coating. PDA-SP can act as a good ligand for cations, forming CA-metal complexes through strong coordination bonds. For PVDF materials, PDA-SP can adhere to the surface by forming covalent and hydrogen bonds, thus strongly adsorbing PDA-SP on the surface of positive electrode materials (LiCoO2 and PVDF), significantly enhancing the hydrophilicity of the material surface. Compared to the surface of the positive electrode material, the hydrophilic groups (-COOH) carried by PDA-SP are less likely to adsorb onto the surface of the negative electrode material graphite. Furthermore, even after PDA-SP adsorbs onto the graphite surface, the adsorption system is unstable, and PDA-SP easily detaches from the surface under strong stirring conditions. Compared to the cathode materials PVDF and LiCoO2, graphite has a relatively lower adsorption capacity for PDA-SP solution and a relatively stronger hydrophobicity, resulting in a sharp increase in the difference in wettability between the two surfaces. This difference leads to changes in the dominant forces between the LiCoO2, PVDF, and graphite surfaces and the collector kerosene. The dominant force on the hydrophilic cathode materials LiCoO2 and PVDF surfaces is electrostatic repulsion, making it difficult for them to adsorb the collector kerosene and prevent it from being carried to the surface by air bubbles. However, a strong hydrophobic attraction still exists between hydrophobic graphite and kerosene. This attraction overcomes the electrostatic repulsion, allowing a large amount of collector kerosene to be adsorbed on the graphite surface, thus achieving the selective separation of the cathode and anode materials.

[0030] On the other hand, the small molecule inhibitor PDA-SP, due to its short molecular chain, can significantly reduce the technical challenge of low concentrate grade caused by gangue entrainment effect during bubble flotation. Attached Figure Description

[0031] Figure 1 The 13C nuclear magnetic resonance spectra of the PDA prepared for this invention and the PDA-SP inhibitor molecules synthesized under different SP concentration conditions.

[0032] Figure 2 Infrared spectra of the PDA prepared in this invention and the PDA-SP inhibitor molecules synthesized under different SP concentration conditions.

[0033] Figure 3 The results show the grade and recovery rate of the cathode material under different inhibitor dosages in Example 3.

[0034] Figure 4 The results show the flotation separation recovery rate and grade in Example 4. Detailed Implementation

[0035] Unless otherwise stated, the terms used herein have the meanings commonly understood by those skilled in the art.

[0036] The technical solution of the present invention will be described in more detail below with reference to embodiments:

[0037] Example 1

[0038] Synthesis of inhibitors

[0039] The steps are as follows:

[0040] S1.2.05g sodium acetate was added to 500ml of deionized water, and the mixture was kept at a constant temperature of 40℃ in an oil bath and stirred for 30min at a stirring speed of 150rpm to obtain a sodium acetate aqueous solution (50mM); the pH of the sodium acetate aqueous solution was adjusted to 5 using hydrochloric acid / sodium hydroxide.

[0041] S2. Add dopamine hydrochloride to an aqueous sodium acetate solution at a dosage of 2 mg / mL, maintain the oil bath temperature at 40°C, stir for 30 min at a stirring speed of 150 rpm, and obtain mixed solution A;

[0042] S3. Add sodium periodate to mixed solution A at a dosage of 4 mg / mL, keep the oil bath at a constant temperature of 40℃, stir for 1 to 4 hours at a stirring speed of 150 rpm to obtain mixed solution B;

[0043] S4. Mixed solution B is left to room temperature to obtain a solution containing the flotation separation inhibitor PDA-SP.

[0044] This inhibitor needs to be prepared and used immediately. The structural formula of its main component is shown in Formula I below. The specific steps for performing carbon NMR spectroscopy on PDA-SP are as follows:

[0045] A certain amount of PDA-SP solution was diluted in CDCl3 solvent to prepare a concentration of approximately 20 mg / mL. The solution was filtered using a 0.2 μm microporous membrane to remove insoluble impurities and prevent interference with the NMR signal. The solution was then transferred to an NMR tube (a standard 5 mm NMR tube), taking care to avoid introducing air bubbles. The NMR tube was filled with 0.7 mL of solution. An NMR spectrometer (Bruker) was then used. 13 C probe, calibrate instrument temperature (approximately 25℃). Select 1000 scans to ensure a sufficiently high signal-to-noise ratio, 90° pulse width, and a delay time of 1-2 seconds to ensure sufficient relaxation of the sample between pulses. Set the spectral width to approximately 200 ppm, and the acquisition time to 0.5-1 second. Monitor the signal in real time during testing to ensure normal data collection. After testing, process the obtained data using software (TopSpin), performing phase correction, baseline correction, and chemical shift (δ) normalization (using the solvent peak, δ = 77.0 ppm for CDCl3). Based on the peak position and intensity of the spectrum, perform chemical shift identification to confirm the structural characteristics of the PDA-SP.

[0046] On the other hand, place the prepared liquid cell on the sample holder of the infrared spectrometer, ensuring that the beam can pass smoothly through the sample. Set the wavenumber range to 2000 cm⁻¹. -1 Up to 1000cm -1 To cover the main absorption peak region of organic compounds, a resolution of 4 cm⁻¹ was selected. -1 To obtain clear absorption peaks, a scan count of 16 was selected to improve the signal-to-noise ratio. The test was initiated, and the infrared spectrum of the sample was recorded. After the scan was completed, the software automatically generated the absorption spectrum. During the test, attention was paid to the solution state to avoid bubbles or uneven solution distribution affecting the test results. After the test, the data was processed using the spectral analysis software OMNIC. Baseline correction was performed to remove possible background interference signals. Based on the position and intensity of the absorption peaks in the spectrum, the characteristic absorption peaks of the PDA-SP compound were determined. The molecular structural characteristics of PDA-SP, such as the presence of functional groups and their vibrational modes, were compared and analyzed with the infrared spectral data of known compounds.

[0047] Analysis of the results of the nuclear magnetic resonance carbon spectrum and infrared spectrum are as follows: Figure 1 and Figure 2 As shown.

[0048]

[0049] Example 2

[0050] Synthesis of inhibitors

[0051] The steps are as follows:

[0052] S1.2.05g sodium acetate was added to 500ml of deionized water, and the mixture was kept at a constant temperature of 40℃ in an oil bath and stirred for 30min at a stirring speed of 150rpm to obtain a sodium acetate aqueous solution (50mM); the pH of the sodium acetate aqueous solution was adjusted to 5 using hydrochloric acid / sodium hydroxide.

[0053] S2. Add dopamine hydrochloride to sodium acetate aqueous solution at a dosage of 4 mg / mL, keep the oil bath at 40℃, stir for 30 min at a stirring speed of 150 rpm to obtain mixed solution A;

[0054] S3. Add sodium periodate to mixed solution A at a dosage of 8 mg / mL, maintain the oil bath temperature at 40℃, stir for 120 min at a stirring speed of 150 rpm to obtain mixed solution B;

[0055] S4. Mixed solution B is left to room temperature to obtain a solution containing the flotation separation inhibitor PDA-SP.

[0056] Example 3

[0057] Flotation separation experiment

[0058] The following steps were taken to separate waste lithium-ion battery positive and negative electrode materials using the flotation separation inhibitor PDA-SP prepared in Example 1:

[0059] S1. The positive and negative electrode materials of the waste lithium-ion batteries come from retired power batteries from Ganfeng Lithium. The positive electrode material is mainly lithium cobalt oxide, and the negative electrode material is mainly graphite. The positive and negative electrode materials are mixed, crushed, and finely ground until the mass percentage of particles smaller than 200 mesh in the material is 85%.

[0060] S2. Using a small flotation machine, take 1g of finely ground material and soak it in an ethanol solution. Stir at 150 rpm for 5 minutes. Then, separate the solid and liquid. Put the solid particles directly into the flotation cell, add 50ml of water and stir for 1 minute at 1500 rpm to obtain the flotation slurry.

[0061] S3. Add 0.05 mg / L flotation separation inhibitor PDA-SP, adjust the slurry for 3 min, and rotate at 1500 rpm;

[0062] S4. Add 80 mg / L collector kerosene, mix for 5 min at 1500 rpm; then add 3 mg / L foaming agent MIBC, mix for 1 min at 1500 rpm.

[0063] S5. Aeration flotation, collecting flotation foam, flotation time is 2 min, 60 plates / min, to obtain flotation concentrate (mainly negative electrode material), and flotation tailings are positive electrode material.

[0064] The collected flotation concentrate and flotation tailings were filtered, dried, and weighed separately. The flotation feedstock and tailings were then subjected to hydrochloric acid leaching, and the Li element content (mass percentage) was determined by IPC. The grade and recovery rate of the cathode material, lithium cobalt oxide, were then calculated.

[0065] The grade of lithium cobalt oxide is calculated as follows: Lithium cobalt oxide grade = Li element content * relative molecular mass of lithium cobalt oxide / relative atomic mass of lithium * 100%.

[0066] The recovery rate of lithium cobalt oxide is calculated as follows: Lithium cobalt oxide recovery rate = (Li content in flotation tailings * mass of flotation feed) / (Li content in flotation feed * mass of flotation feed) * 100%.

[0067] Figure 3 The grades and recoveries of cathode materials under different inhibitor dosages are shown. It can be seen that with increasing inhibitor dosage, the recovery rate of the cathode material initially increases rapidly, reaches a peak, and then decreases, while the grade of the cathode material initially decreases and then increases rapidly. Considering both recovery rate and grade, an inhibitor dosage of 0.05 mg / L is the optimal point.

[0068] Example 4

[0069] The reagent formulation and technical process in this separation experiment were exactly the same as in Example 3, except that the inhibitor dosage was 0.05 mg / L, and the raw materials from retired batteries were replaced with three main representative materials: lithium iron phosphate, lithium manganese oxide, and 811 ternary lithium. The flotation separation recovery rate and grade results are as follows: Figure 4 As shown.

[0070] The flotation separation results show that the flotation separation inhibitor provided by this invention has universal applicability for the selective separation of positive / negative electrode materials from waste lithium-ion batteries from different sources.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flotation separation reagent for positive and negative electrode materials of waste batteries, characterized in that, The drug is named PDA, and its structural formula is shown in formula (Ⅰ): （Ⅰ）。 2. A flotation separation inhibitor for positive and negative electrode materials of waste batteries, characterized in that, The flotation separation inhibitor comprises the reagent PDA as described in claim 1.

3. A method for preparing the flotation separation inhibitor for positive and negative electrode materials of waste batteries as described in claim 2, characterized in that, Includes the following steps: S1. Prepare an aqueous solution of sodium acetate, and adjust the pH of the sodium acetate aqueous solution to 4.5~5.5 using hydrochloric acid; S2. Add the set amount of dopamine hydrochloride to the sodium acetate aqueous solution, stir to dissolve, and obtain mixed solution A; S3. Add the set amount of sodium periodate to mixed solution A, stir to dissolve, and obtain mixed solution B; S4. The mixed solution B is placed at room temperature to obtain a flotation separation inhibitor containing the reagent PDA, which is named PDA-SP.

4. The method for preparing the flotation separation inhibitor for positive and negative electrode materials of waste batteries as described in claim 3, characterized in that, The concentration of the sodium acetate aqueous solution is 50~100 mM.

5. The method for preparing the flotation separation inhibitor for positive and negative electrode materials of waste batteries as described in claim 3, characterized in that, The dosage of dopamine hydrochloride is 1~4 mg / mL, and the mixture is stirred for 30 min at a stirring speed of 150 rpm.

6. The method for preparing the flotation separation inhibitor for positive and negative electrode materials of waste batteries as described in claim 3, characterized in that, The amount of sodium periodate used is 2~8 mg / mL, and the reaction is stirred for 1~4 hours at a stirring speed of 150 rpm.

7. The method for preparing a flotation separation inhibitor for positive and negative electrode materials of waste batteries as described in claim 3, characterized in that, In steps S1-S4, the system temperature is 20~40℃.

8. The application of a flotation separation inhibitor prepared by the method according to any one of claims 3-6 in the flotation recovery of positive and negative electrode materials of waste lithium-ion batteries, characterized in that, Includes the following steps: S1. Waste lithium-ion battery positive and negative electrode materials are mixed, crushed, and finely ground until the mass percentage of particles with a size of less than 200 mesh in the material is ≥85%; S2. After being soaked in ethanol, the finely ground material is separated, fed into a flotation cell, and water is added to adjust the slurry to obtain flotation slurry; S3. Add the flotation separation inhibitor PDA-SP at a concentration of 0.05 mg / L, rotate at 1500 rpm, and adjust the slurry for 3 minutes. S4. Continue stirring, add the collector and foaming agent in sequence, and stir to adjust the slurry for the set time; S5. Aeration flotation, collecting flotation foam to obtain negative electrode material; collecting flotation tailings, i.e., positive electrode material.

9. The application of the flotation separation inhibitor as described in claim 8 in the flotation recovery of positive and negative electrode materials of waste lithium-ion batteries, characterized in that, In step S2, the finely ground material is immersed in an ethanol solution and stirred at 150 rpm for 5 minutes to separate the solid and liquid. The material is then placed in a flotation cell and mixed with water at a ratio of 1 g: 50 ml. The mixture is stirred at 1500 rpm for 1 minute to obtain the flotation slurry.

10. The application of the flotation separation inhibitor as described in claim 8 in the flotation recovery of positive and negative electrode materials of waste lithium-ion batteries, characterized in that, In step S4, the collector is kerosene, added at a rate of 80 mg / L, and the mixture is prepared for 5 min at a speed of 1500 rpm; the foaming agent is methyl isobutyl methanol, added at a rate of 3 mg / L, and the mixture is prepared for 1 min at a speed of 1500 rpm.

Images