Waste battery positive and negative electrode material flotation separation reagent, inhibitor and preparation method and application of waste battery positive and negative electrode material flotation separation reagent

Abstract

The invention belongs to the technical field of retired power battery recovery, and particularly relates to a flotation separation reagent and inhibitor for waste battery positive and negative electrode materials and a preparation method and application of the flotation separation reagent and inhibitor. The flotation separation reagent is named PDA, and the structural formula of the flotation separation reagent is as shown in the formula I: # imgabs0. The invention further provides a preparation method for preparing the PDA-containing flotation inhibitor PDA-SP. The brand-new micromolecular organic inhibitor PDA is provided through a chemical synthesis method, the molecular chain of the inhibitor is short, and the surface wettability difference of the waste battery positive and negative electrode materials can be changed through selective adsorption, so that the flotation separation efficiency of the waste battery positive and negative electrode materials is improved; and the method has important significance for developing a more efficient and environment-friendly battery recovery process.

Description

Technical Field

[0001] The present invention belongs to the technical field of retired power battery recycling, and specifically relates to a flotation separation agent for positive and negative electrode materials of waste batteries, a flotation separation inhibitor, and a preparation method and application thereof. Background Art

[0002] The recycling of retired batteries is an important issue in environmental protection and resource regeneration. The efficient separation of positive electrode graphite and negative electrode ternary lithium / lithium cobalt oxide materials is of great significance for the reuse of waste batteries.

[0003] As an effective physical separation technology, flotation can achieve the selective separation of different materials by regulating the surface chemical properties of minerals. The positive electrode materials of discarded lithium-ion batteries are mainly ternary lithium / lithium cobalt oxide / lithium iron phosphate, and the negative electrode materials are usually graphite. Graphite is a non-polar mineral with good hydrophobicity, while ternary lithium / lithium cobalt oxide / lithium iron phosphate are ionic crystals with strong hydrophilicity. From the perspective of flotation theory, it is feasible to use flotation to separate positive and negative electrode materials through the difference in surface hydrophilicity. However, due to the presence of the binder polyvinylidene fluoride (PVDF) on the surface of the positive electrode material, its surface becomes extremely hydrophobic, making it difficult to separate the positive and negative electrode materials, and the recovery rate and grade are low.

[0004] Therefore, the research of new flotation depressants plays a key role in this process. Its mechanism of action is mainly to improve the flotation separation efficiency and selectivity by selectively adsorbing the depressants and changing the surface wettability differences of the materials. At present, most studies use organic depressants, such as carboxymethyl cellulose, gum arabic, starch, etc. However, due to the long carbon chain, these organic depressants are easy to agglomerate between particles, resulting in many inclusions of gangue minerals and low grade of target minerals; in addition, these organic depressants have poor adsorption selectivity and low recovery rate of key materials.

[0005] Therefore, providing a new 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 needs to be solved urgently. Summary of the invention

[0006] In order to solve the above technical problems, one of the purposes of the present invention is to provide a flotation separation agent for positive and negative electrode materials of waste batteries.

[0007] The technical solution adopted by the present invention is as follows:

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

[0009]

[0010] The second object of the present invention is to provide a flotation separation inhibitor for positive and negative electrode materials of waste batteries, wherein the flotation separation inhibitor comprises the agent PDA as claimed in claim 1

[0011] The third object of the present invention is to provide a method for preparing the above-mentioned waste battery positive and negative electrode material flotation separation inhibitor, comprising the following steps:

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

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

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

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

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

[0017] Preferably, the dosage of dopamine hydrochloride is 1-4 mg / mL, stirring is carried out for 30 minutes, and the stirring speed is 150 rpm.

[0018] Preferably, the dosage of sodium periodate 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°C.

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

[0021] S1. Mix and crush the positive and negative electrode materials of discarded lithium-ion batteries, and grind them into particles with a size less than 200 mesh, accounting for ≥85% by mass;

[0022] S2. The finely ground material is soaked in ethanol, separated, put into a flotation tank, and water is added to obtain a flotation pulp;

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

[0024] S4. Continue stirring, add the collector and frother in sequence and stir the slurry for a set time;

[0025] S5. Aerate flotation, collect flotation foam to obtain negative electrode materials; collect flotation tailings, which are positive electrode materials.

[0026] Preferably, in step S2, the finely ground material is immersed in an ethanol solution, stirred at a speed of 150 rpm for 5 minutes, solid-liquid separation is performed, and the material is put into a flotation tank, water is added according to 1 g:50 ml for slurry preparation, the speed is 1500 rpm, and the material is stirred for 1 minute to obtain flotation pulp.

[0027] Preferably, in step S4, the collector is kerosene, added in an amount of 80 mg / L, slurry mixing for 5 minutes, and a rotation speed of 1500 rpm; the foaming agent is methyl isobutyl carbinol MIBC, added in an amount of 3 mg / L, slurry mixing for 1 minute, and a rotation speed of 1500 rpm.

[0028] The beneficial effects of the present invention are:

[0029] This patent realizes the development of small molecule organic inhibitors through chemical synthesis. The inhibitor has short molecular chains and strong selectivity, which can effectively improve the flotation separation efficiency of the positive and negative electrode materials of retired power batteries. First, PDA-SP is used as a selective flotation inhibitor to separate lithium-containing active materials / PVDF and negative electrode materials graphite in 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 and form CA-metal complexes through strong coordination bonds. For PVDF materials, PDA-SP can attach to the surface by forming covalent bonds and hydrogen bonds, so the surface of the positive electrode material (LiCoO2 and PVDF) can strongly adsorb PDA-SP, and the hydrophilicity of the material surface is significantly enhanced. Compared with the surface of the positive electrode material, the hydrophilic group (-COOH) carried by PDA-SP is less likely to be adsorbed on the surface of the negative electrode material graphite. In addition, even after PDA-SP is adsorbed on the graphite surface, the adsorption system is unstable, and PDA-SP is easy to fall off the surface in a strong stirring environment. Compared with the positive electrode materials PVDF and LiCoO2, the graphite surface has a relatively small adsorption capacity for PDA-SP solution, and its hydrophobicity is relatively strong, and the difference in wettability between the two surfaces increases sharply. This difference leads to changes in the dominant force between the LiCoO2, PVDF and graphite surfaces and the collector kerosene. The dominant force on the hydrophilic positive electrode materials LiCoO2 and PVDF surfaces is electrostatic repulsion, which makes it difficult for the LiCoO2 and PVDF surfaces to adsorb the collector kerosene and cannot be carried up by bubbles; however, there is still a huge hydrophobic attraction 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, thereby achieving the goal of selective separation of positive and negative electrode materials.

[0030] On the other hand, the small molecule inhibitor PDA-SP can significantly reduce the technical difficulty of low concentrate grade caused by the gangue entrainment effect in the bubble flotation process due to its short molecular chain. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0033] Figure 3 The results of the grade and recovery rate of the positive electrode material under different inhibitor dosage conditions in Example 3.

[0034] Figure 4 The flotation separation recovery rate and grade results in Example 4. DETAILED DESCRIPTION

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

[0036] The technical solution of the present invention is described in more detail below in conjunction with the embodiments:

[0037] Example 1

[0038] Synthesis of inhibitors

[0039] Here are the steps:

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

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

[0042] S3. Sodium periodate was added to the mixed solution A in an amount of 4 mg / mL, the mixture was kept at a constant temperature of 40°C in an oil bath, and the reaction was stirred for 1 to 4 hours at a stirring speed of 150 rpm to obtain a mixed solution B;

[0043] S4. The mixed solution B is allowed to cool to room temperature to obtain a solution containing the flotation separation inhibitor PDA-SP.

[0044] The inhibitor needs to be prepared and used immediately, and the main component structure is shown in Formula I below. The PDA-SP is tested by carbon nuclear magnetic resonance spectrum, and the specific steps are:

[0045] A certain amount of PDA-SP solution was diluted in CDCl3 solvent, and the prepared concentration was generally 20 mg / mL. The solution was filtered through a microporous filter membrane (0.2 μm) to remove insoluble impurities to prevent the NMR signal from being affected. The solution was transferred to an NMR tube (5 mm standard NMR tube) to avoid introducing bubbles. The NMR tube was filled with 0.7 mL of solution. A NMR spectrometer (Bruker) was used, equipped with 13 C probe, calibrate the instrument temperature (about 25°C). Select 1000 scans to ensure that the signal-to-noise ratio is high enough, 90° pulse width, and delay time of 1-2 seconds to ensure sufficient relaxation of the sample between pulses. The spectrum width is set to about 200ppm, and the acquisition time is usually set to 0.5-1 second. During the test, monitor the signal in real time to ensure normal data collection. After the test, use software (TopSpin) to process the obtained data, perform phase correction, baseline correction, and standardize the chemical shift (δ) (using the solvent peak, δ of CDCl3 = 77.0ppm). According to the peak position and intensity of the spectrum, chemical shift identification is performed to confirm the structural characteristics of PDA-SP.

[0046] On the other hand, place the prepared liquid cell on the sample holder of the infrared spectrometer to ensure that the beam can pass through the sample smoothly. The wavenumber range is set to 2000cm -1 Up to 1000cm -1 , to cover the main absorption peak area of ​​organic compounds. The resolution is selected as 4cm -1 , to obtain a clear absorption peak. Select 16 scans to improve the signal-to-noise ratio. Start the test and record the infrared spectrum of the sample. After the scan is completed, the software automatically generates an absorption spectrum. During the test, pay attention to the state of the solution to avoid bubbles or uneven distribution of the solution affecting the test results. After the test is completed, use the spectral analysis software OMNIC to process the data. Perform baseline correction to remove possible background interference signals. Determine the characteristic absorption peak of the PDA-SP compound based on the absorption peak position and intensity of the spectrum. Refer to the infrared spectrum data of known compounds to compare and analyze the molecular structure characteristics of PDA-SP, such as the presence of functional groups and their vibration modes.

[0047] The results of the carbon NMR spectrum and infrared spectrum are as follows: Figure 1 and Figure 2 shown.

[0048]

[0049] Example 2

[0050] Synthesis of inhibitors

[0051] Here are the steps:

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

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

[0054] S3. Sodium periodate was added to the mixed solution A in an amount of 8 mg / mL, the mixture was kept at a constant temperature of 40°C in an oil bath, stirred for 120 min at a stirring speed of 150 rpm to obtain a mixed solution B;

[0055] S4. The mixed solution B is allowed to cool to room temperature to obtain a solution containing the flotation separation inhibitor PDA-SP.

[0056] Example 3

[0057] Flotation separation experiment

[0058] The flotation separation inhibitor PDA-SP prepared in Example 1 is used to separate the positive and negative electrode materials of waste lithium-ion batteries, and the steps are as follows:

[0059] S1. The positive and negative electrode materials of discarded lithium-ion batteries come from retired power batteries of 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 and crushed, and finely ground until the mass proportion of the material with a particle size of less than 200 mesh is 85%;

[0060] S2. Using a small flotation machine, 1g of finely ground material was pre-soaked in an ethanol solution, stirred at a speed of 150rpm for 5min, and then the solid-liquid separation was performed. The solid particles were directly put into the flotation tank, and 50ml of water was added and stirred for 1min at a speed of 1500rpm to obtain a flotation pulp;

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

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

[0063] S5. Aerate flotation, collect flotation foam, scrape foam time is 2min, 60 plates / min, 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. The flotation raw materials and flotation tailings were leached with hydrochloric acid, and the Li element content (mass percentage) was determined by IPC, and then the grade and recovery rate of the positive electrode material lithium cobalt oxide were 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: recovery rate of lithium cobalt oxide = (Li element content in flotation tailings*mass of flotation raw materials) / (Li element content in flotation raw materials*mass of flotation raw materials)*100%.

[0067] Figure 3 The following are the grade and recovery rate of the positive electrode material under different inhibitor dosage conditions. It can be seen that with the increase of inhibitor dosage, the recovery rate of the positive electrode material shows a trend of first increasing rapidly, reaching the highest point and then decreasing, while the grade of the positive electrode material decreases first and then increases rapidly. Considering the recovery rate and grade comprehensively, the best point is when the inhibitor dosage is 0.05 mg / L.

[0068] Example 4

[0069] The reagent system and technical process in this separation experiment are exactly the same as those in Example 3, except that the inhibitor dosage is 0.05 mg / L, and the retired battery raw materials are 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 shown in Figure 2. Figure 4 shown.

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

[0071] The above are only preferred practical examples of the present invention and are not intended to limit the invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill 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 in the protection scope of the present invention.

Claims

1. A flotation separation agent for waste battery positive and negative electrode materials, characterized in that: The drug is named PDA, and its structural formula is shown in formula (I):

2. A flotation separation inhibitor for positive and negative electrode materials of waste batteries, characterized in that: The flotation separation inhibitor comprises the pharmaceutical agent PDA as claimed in claim 1.

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

4. The method for preparing the flotation separation inhibitor for positive and negative electrode materials of waste batteries according to 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 according to claim 3, characterized in that: The dosage of dopamine hydrochloride is 1-4 mg / mL, stirring is performed for 30 minutes, and the stirring speed is 150 rpm.

6. The method for preparing the flotation separation inhibitor for positive and negative electrode materials of waste batteries according to claim 3, characterized in that: The dosage of sodium periodate 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 according to claim 3, characterized in that: In the steps S1-S4, the system temperature is 20-40°C.

8. Use of the flotation separation inhibitor prepared by the preparation method according to any one of claims 3 to 6 in flotation recovery of positive and negative electrode materials of waste lithium-ion batteries, characterized in that: The following steps are involved: S1. Mix and crush the positive and negative electrode materials of discarded lithium-ion batteries, and grind them into particles with a size less than 200 mesh, accounting for ≥85% by mass; S2. The finely ground material is soaked in ethanol, separated, put into a flotation tank, and water is added to obtain a flotation pulp; S3. Add 0.05 mg / L of flotation separation inhibitor PDA-SP, rotate at 1500 rpm, and mix for 3 minutes. S4. Continue stirring, add the collector and frother in sequence and stir the slurry for a set time; S5. Aerate flotation, collect flotation foam to obtain negative electrode materials; collect flotation tailings, which are positive electrode materials.

9. The use of the flotation separation inhibitor prepared by the preparation method of claim 3 in flotation recovery of positive and negative electrode materials of waste lithium-ion batteries as claimed in claim 8, characterized in that: In step S2, the finely ground material is immersed in an ethanol solution, stirred at a speed of 150 rpm for 5 minutes, solid-liquid separation is performed, and the material is put into a flotation tank, water is added according to 1g:50ml for slurry preparation, the speed is 1500 rpm, and the material is stirred for 1 minute to obtain flotation pulp.

10. The use of the flotation separation inhibitor prepared by the preparation method of claim 3 as claimed in claim 8 in the flotation method for recovering positive and negative electrode materials of waste lithium-ion batteries, characterized in that: In step S4, the collector is kerosene, the addition amount is 80 mg / L, the slurry is mixed for 5 minutes, and the rotation speed is 1500 rpm; the foaming agent is methyl isobutyl carbinol, the addition amount is 3 mg / L, the slurry is mixed for 1 minute, and the rotation speed is 1500 rpm.

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