Method for separating ncm and lfp from ncm / lfp mixed black powder

Abstract

The application provides a method for separating NCM and LFP from NCM / LFP mixed black powder, comprising: oxidizing and roasting the mixed black powder to convert LFP into LFP roasting particles; adding LFP inhibitors and NCM collectors into the mixed black powder after the oxidation and roasting, in sequence, to make NCM particles hydrophobic independently of the LFP roasting particles under alkaline conditions; adding emulsified oil to make the hydrophobic NCM particles agglomerate under mechanical shearing to form NCM agglomerates; and grading the NCM agglomerates and the LFP roasting particles according to particle size difference to prepare mutually separated NCM and LFP. The method for separating NCM and LFP from NCM / LFP mixed black powder provided by the application solves the problem that two kinds of mixed materials with similar surface properties of LFP and NCM are difficult to separate by physical methods through the synergistic cooperation of oxidation and roasting, selective hydrophobicization, selective agglomeration and particle size grading.

Description

Technical Field

[0001] This application relates to the field of battery recycling technology, specifically to a method for separating NCM and LFP from NCM / LFP mixed black powder. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the demand for recycling retired power batteries is becoming increasingly urgent. Lithium iron phosphate (LFP) and lithium nickel cobalt manganese oxide (NCM) are currently the two mainstream cathode materials for power batteries, and they often coexist in retired batteries as a mixed black powder. Therefore, developing an efficient separation method for the two cathode materials in LFP and NCM mixed black powder is of great significance for ensuring resource recycling.

[0003] Currently, the separation methods for LFP and NCM mixed black powders are mainly divided into two categories: hydrometallurgical and physical methods. While hydrometallurgical methods can achieve elemental separation of valuable metals, they suffer from problems such as long process flows, high consumption of chemical reagents, and high wastewater treatment costs. Physical methods, on the other hand, have attracted much attention due to their shorter process flow and lower cost. However, on the one hand, both LFP and NCM are micron-sized particles with similar initial surface wettability and surface electrical properties, making selective separation difficult through physical sorting. On the other hand, the fine particle size of the mixed black powder makes physical sorting methods ineffective for separating fine-sized materials, hindering the direct and simultaneous acquisition of high-grade and high-recovery separated products. Furthermore, traditional physical sorting methods often require surface modification or particle size expansion when processing fine-sized materials. However, the introduction of these methods can easily lead to particle breakage or changes in surface properties during subsequent dissociation or dispersion processes, affecting the sorting effect and product quality. These problems make it difficult for traditional physical methods to meet industrial-scale requirements in terms of separation purity and recovery rate for LFP and NCM mixed black powders. Summary of the Invention

[0004] In view of this, this application provides a method for separating NCM and LFP from NCM / LFP mixed black powder. The method combines the steps of creating surface chemical differences through oxidative roasting, selectively establishing hydrophobic differences through inhibitors and collectors, amplifying the agglomeration of emulsified oil into particle size differences, and graded separation. This solves the technical problem that it is difficult to selectively separate two fine particle mixtures of LFP and NCM with similar surface properties through physical methods.

[0005] To achieve the above objectives, in a first aspect, this application provides a method for separating NCM and LFP from a mixed NCM / LFP black powder, comprising the following steps: oxidizing and calcining the mixed black powder to convert LFP into calcined LFP particles; sequentially adding an LFP inhibitor and an NCM collector to the oxidized and calcined mixed black powder, and under alkaline conditions, hydrophobizing the NCM particles independently of the LFP calcined particles; adding emulsified oil to cause the hydrophobic NCM particles to agglomerate under mechanical shearing, forming NCM agglomerates, and creating a particle size difference between the NCM agglomerates and the LFP calcined particles; and using the particle size difference to classify the NCM agglomerates and LFP calcined particles to prepare mutually separated NCM and LFP.

[0006] Based on the first aspect, in some embodiments, the oxidative calcination temperature is 480℃~550℃ and the time is 90min~150min.

[0007] Based on the first aspect, in some embodiments, the pH of the alkaline conditions is 8.0 to 9.0.

[0008] Based on the first aspect, in some embodiments, the LFP inhibitor includes modified starch and / or dextrin.

[0009] Based on the first aspect, in some embodiments, the NCM collector includes one or more of benzohydroxyxamic acid, salicylic acid, phthalic acid, octylhydroxyxamic acid, and isobutylhydroxyxamic acid.

[0010] Based on the first aspect, in some embodiments, the amount of LFP inhibitor used is 150 g / t to 300 g / t based on the dry weight of the mixed black powder.

[0011] Based on the first aspect, in some embodiments, the amount of NCM collector used is 150 g / t to 250 g / t based on the dry weight of the mixed black powder.

[0012] Based on the first aspect, in some embodiments, the amount of emulsified oil used is 500 g / t to 1500 g / t, based on the dry weight of the mixed black powder.

[0013] Based on the first aspect, in some embodiments, the linear velocity of mechanical shearing is 15 m / s to 25 m / s, and the processing time is 5 min to 10 min.

[0014] Based on the first aspect, in some embodiments, the emulsified oil includes one or more of kerosene, diesel oil, paraffin oil, light white oil, naphthenic oil, and transformer oil.

[0015] Based on the first aspect, in some embodiments, NCM aggregates are collected as underflow products and LFP calcined particles are collected as overflow products.

[0016] Based on the first aspect, in some embodiments, after separating the NCM aggregates from the LFP calcined particles by the difference in hydrophobicity, the method further includes: chemically depolymerizing the separated NCM aggregates under the action of a demulsifier.

[0017] Based on the first aspect, in some embodiments, the demulsifier includes a short-chain alcohol having 3 to 8 carbon atoms.

[0018] Based on the first aspect, in some embodiments, the amount of demulsifier used is 100 g / t to 200 g / t based on the dry weight of the mixed black powder.

[0019] Based on the first aspect, in some embodiments, the method further includes: performing microbubble flotation treatment on the chemically depolymerized slurry.

[0020] Compared to traditional technologies, the advantages of this application are as follows:

[0021] The method for separating NCM and LFP from a mixed NCM / LFP black powder provided in this application involves oxidatively calcining the mixed black powder to convert LFP into calcined LFP particles. At this point, the calcined LFP particles and NCM particles exhibit different surface chemical properties. Based on this, an LFP inhibitor and an NCM collector are added sequentially while maintaining the system under alkaline conditions. The first added LFP inhibitor selectively adsorbs onto the surface of the calcined LFP particles, inhibiting their flotation. The subsequently added NCM collector causes the NCM particles to hydrophobize independently of the calcined LFP particles, thereby... A hydrophobic difference that allows for separation is established between two types of particles with similar surface properties. Then, emulsified oil is added, and under mechanical shearing, the hydrophobic NCM particles selectively aggregate through oil bridging to form NCM agglomerates. These NCM particles exist in agglomerated form with relatively large particle sizes, while the unhydrophobicated LFP calcined particles retain their original fine particle size. This creates a particle size difference that allows for physical separation between the NCM agglomerates and the LFP calcined particles. This particle size difference is then used for fractionation to obtain products enriched with NCM and products enriched with LFP, respectively.

[0022] The method for separating NCM and LFP from NCM / LFP mixed black powder provided in this application achieves physical separation of NCM and LFP through the synergistic combination of four steps: oxidative roasting, selective hydrophobication, selective agglomeration, and particle size classification. This eliminates the need for hydrometallurgical processes such as acid leaching and extraction, simplifying the separation process and reducing reagent consumption and wastewater treatment costs. Furthermore, compared to direct flotation methods that rely on differences in the natural surface properties of particles, this application actively creates surface chemical differences through oxidative roasting combined with agglomeration amplification, reducing the risk of ineffective separation of fine-grained materials due to their small particle size. This facilitates achieving good separation results within a wider operating window. Detailed Implementation

[0023] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions will be provided below. The technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the technical solutions of this application more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] One embodiment of this application provides a method for separating NCM and LFP from an NCM / LFP mixed black powder, comprising the following steps:

[0026] Step 1: Oxidize and roast the mixed black powder to convert LFP into LFP roasted particles.

[0027] In the above steps, LFP is converted into LFP calcined particles by oxidizing and calcining the mixed black powder. At this time, the LFP calcined particles and NCM particles have different surface chemical properties.

[0028] In some embodiments, the oxidation calcination temperature is 480℃~550℃, and the time is 90 min~150 min. For example, the oxidation calcination temperature can be 480℃, 485℃, 490℃, 495℃, 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, 535℃, 540℃, 545℃, 550℃, or any value within the range of any two of the above values; the oxidation calcination time can be 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 120 min, 125 min, 130 min, 135 min, 140 min, 145 min, 150 min, or any value within the range of any two of the above values. Furthermore, controlling the temperature and time of oxidative calcination within the aforementioned range helps to fully disrupt the olivine structure of LFP in the mixed black powder and transform it into a mixed calcination product such as Li3Fe2(PO4)3 and Fe2O3. This introduces sufficient surface chemical differences between the calcined LFP particles and NCM particles, which is beneficial for the selective adsorption of subsequent inhibitors. Simultaneously, controlling the temperature range also helps to reduce the risk of excessive remodeling of the NCM particle surface at higher calcination temperatures, thus reducing the chelating adsorption sites for collectors. Controlling the calcination time within the aforementioned range helps to ensure sufficient LFP oxidative conversion and also helps to control process energy consumption.

[0029] Step 2: Add LFP inhibitor and NCM collector to the mixed black powder after oxidative roasting in sequence. Under alkaline conditions, make the NCM particles hydrophobic independently of the LFP roasted particles.

[0030] In the above steps, taking advantage of the difference in surface chemical properties between LFP calcined particles and NCM particles produced by oxidative calcination, LFP inhibitors and NCM collectors are added sequentially while the system is controlled under alkaline conditions. The LFP inhibitors added first can selectively adsorb onto the surface of LFP calcined particles to inhibit their flotation, while the NCM collectors added later can make the NCM particles hydrophobic independently of the LFP calcined particles, thereby establishing a hydrophobic difference that can be separated between the two particles with similar surface properties.

[0031] In some embodiments, the pH of the alkaline conditions is 8.0–9.0. For example, the pH of the alkaline conditions can be 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, or any value within the range of any two of the above values. Further, by controlling the alkaline pH of the system within the above range, the LFP calcined product (containing Fe2O3) carries an appropriate amount of negative charge on its surface, which facilitates the selective adsorption of the LFP inhibitor onto the surface of the LFP calcined particles through hydrogen bonding and electrostatic forces, thereby exerting an inhibitory effect. Simultaneously, under this pH condition, the NCM particle surface still retains sufficient metal active sites for chelation coordination by the NCM collector, thus achieving a balance between inhibiting the LFP calcined particles and collecting NCM.

[0032] In some embodiments, the LFP inhibitor comprises modified starch and / or dextrin. Further, using modified starch or dextrin as the inhibitor, which possesses strong hydrophilicity and selective adsorption capacity, facilitates the formation of a hydrophilic film layer on the surface of the LFP calcined particles.

[0033] In some embodiments, the NCM collector includes one or more of benzohydroxyxamic acid, salicylic acid, phthalic acid, octylhydroxyxamic acid, and isobutylhydroxyxamic acid. Preferably, the NCM collector includes benzohydroxyxamic acid. Further, using benzohydroxyxamic acid as a chelating collector allows its hydroxyxamic group to form stable five-membered ring chelates with metal ions such as Ni, Co, and Mn on the surface of NCM particles, which is beneficial for forming a robust hydrophobic adsorption layer on the surface of NCM particles.

[0034] In some embodiments, the dosage of LFP inhibitor is 150 g / t to 300 g / t based on the dry weight of the mixed black powder. For example, based on the dry weight of the mixed black powder, the dosage of LFP inhibitor can be 150 g / t, 160 g / t, 170 g / t, 180 g / t, 190 g / t, 200 g / t, 210 g / t, 220 g / t, 230 g / t, 240 g / t, 250 g / t, 260 g / t, 270 g / t, 280 g / t, 290 g / t, 300 g / t, or any value within the range of any two of the above values. Furthermore, controlling the dosage of LFP inhibitor (such as modified starch and / or dextrin) within the above range helps to form a complete but not excessive inhibition layer on the surface of the LFP roasted particles, ensuring that the iron-containing phase is sufficiently inhibited and reducing the risk of excessive inhibitor residues in the slurry, which weakens the adsorption effect of the collector.

[0035] In some embodiments, the amount of NCM collector used is 150 g / t to 250 g / t based on the dry weight of the mixed black powder. For example, the amount of NCM collector used can be 150 g / t, 160 g / t, 170 g / t, 180 g / t, 190 g / t, 200 g / t, 210 g / t, 220 g / t, 230 g / t, 240 g / t, or 250 g / t, or any value within the range of any two of the above values. Furthermore, controlling the amount of NCM collector (such as benzohydroxyxamic acid) within the above range is beneficial for forming a sufficiently dense hydrophobic adsorption layer on the surface of NCM particles, enabling the NCM particles to obtain suitable surface hydrophobicity and aggregation activity, while also helping to reduce reagent waste and selectivity reduction when there is too much collector.

[0036] Step 3: Add emulsified oil to cause the hydrophobic NCM particles to agglomerate under mechanical shearing, forming NCM agglomerates. The NCM agglomerates and LFP calcined particles have a particle size difference.

[0037] In the above steps, taking advantage of the difference in hydrophobicity between LFP calcined particles and hydrophobic NCM particles, emulsified oil is added and under mechanical shearing, the hydrophobic NCM particles selectively agglomerate through oil bridging to form NCM agglomerates, so that the NCM particles exist in agglomerated form with a relatively large particle size, while the non-hydrophobicated LFP calcined particles retain their original fine particle size. Thus, a particle size difference that can be physically separated is generated between the NCM agglomerates and the LFP calcined particles.

[0038] In some embodiments, the emulsified oil includes one or more of kerosene, diesel oil, paraffin oil, light white oil, naphthenic oil, and transformer oil. Preferably, the emulsified oil includes kerosene.

[0039] In some embodiments, the amount of emulsified oil used is 500 g / t to 1500 g / t based on the dry weight of the mixed black powder. For example, based on the dry weight of the mixed black powder, the amount of emulsified oil used can be 500 g / t, 600 g / t, 700 g / t, 800 g / t, 900 g / t, 1000 g / t, 1100 g / t, 1200 g / t, 1300 g / t, 1400 g / t, 1500 g / t, or any value within the range of any two of the above values. Furthermore, controlling the amount of emulsified oil within the above range allows for the formation of a sufficient number of emulsified oil droplets in the slurry, providing a sufficient bridging medium for oil bridge connections between hydrophobic NCM particles, which is beneficial for forming NCM agglomerates with stable structures and appropriate particle sizes. Simultaneously, it helps reduce the risk of insufficient agglomeration when the amount of emulsified oil is too small, or excessively strong oil bridges when the amount is too large, increasing the difficulty of subsequent deagglomeration.

[0040] In some embodiments, the linear velocity of the mechanical shearing is 15 m / s to 25 m / s, and the processing time is 5 min to 10 min. For example, the linear velocity of the mechanical shearing can be 15 m / s, 16 m / s, 17 m / s, 18 m / s, 19 m / s, 20 m / s, 21 m / s, 22 m / s, 23 m / s, 24 m / s, 25 m / s, or any value within the range of any two of the above values; the processing time of the mechanical shearing can be 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, 10 min, or any value within the range of any two of the above values. Furthermore, controlling the linear velocity of mechanical shearing within the aforementioned range helps the slurry to be in a suitable shear force field, which is beneficial for the uniform dispersion of emulsified oil droplets in the slurry and for sufficient collision and contact with hydrophobic NCM particles. It also helps to avoid excessive shear force from damaging the already formed NCM agglomerate structure. At the same time, controlling the mechanical shearing time within the aforementioned range helps to ensure that the agglomeration process between hydrophobic NCM particles is fully carried out, forming NCM agglomerates with suitable particle size and strength, and also helps to control the process cycle.

[0041] Step 4: Classify NCM agglomerates and LFP calcined particles by utilizing particle size differences to prepare mutually separated NCM and LFP.

[0042] In the above steps, the particle size difference between NCM agglomerates and LFP calcined particles is used for classification, and NCM-enriched products and LFP-enriched products can be obtained respectively.

[0043] In some embodiments, NCM aggregates are collected as underflow products and LFP calcined particles as overflow products. Understandably, during the fractionation process, NCM aggregates, due to their relatively large particle size, tend to exist as underflow products, while LFP calcined particles, with their relatively small particle size, tend to exist as overflow products. Therefore, the separation method of this application, by gradually building property differences between NCM and LFP, ultimately leads to a clear particle size difference between NCM and LFP. Utilizing this particle size difference for fractionation helps reduce the risk of cross-contamination between products, achieving good separation of NCM and LFP in NCM / LFP mixed black powder.

[0044] In some embodiments, after separating NCM aggregates from LFP calcined particles by difference in hydrophobicity, the process further includes: chemically depolymerizing the separated NCM aggregates under the action of a demulsifier. In some embodiments, the demulsifier includes short-chain alcohols with 3 to 8 carbon atoms. For example, short-chain alcohols include, but are not limited to, one or more of 2-octanol, isopropanol, and n-butanol. Further, in this application, after NCM aggregates are collected in stages, they can be treated with a demulsifier. For example, short-chain alcohol molecules can reduce the oil-water interfacial tension formed by the emulsified oil and penetrate into the interior of the oil bridge structure, causing the oil bridges that maintain the aggregation between NCM particles to disintegrate gently, thereby restoring the NCM aggregates to a single-particle state. Compared with physical depolymerization using high shear force, chemical depolymerization helps to avoid damage to the particle crystal structure and mechanical desorption of the surface collector adsorption layer caused by mechanical force, thereby retaining a high proportion of benzo[a]hydroxyxamic acid collector on the surface of the depolymerized NCM particles, preserving a good hydrophobic surface for possible subsequent processing (such as secondary selection).

[0045] In some embodiments, the amount of demulsifier used is 100 g / t to 200 g / t based on the dry weight of the mixed black powder. For example, based on the dry weight of the mixed black powder, the amount of demulsifier used can be 100 g / t, 110 g / t, 120 g / t, 130 g / t, 140 g / t, 150 g / t, 160 g / t, 170 g / t, 180 g / t, 190 g / t, 200 g / t, or any value within the range of any two of the above values. Furthermore, controlling the amount of demulsifier (such as short-chain alcohol) within the above range is beneficial for providing sufficient demulsifying active material to achieve the gentle disintegration of oil bridges, while reducing the risk of excessive demulsifier residue in the slurry affecting subsequent processes.

[0046] In some embodiments, the method further includes microbubble flotation treatment of the chemically depolymerized slurry. Further, this application has found that in the chemically depolymerized slurry, NCM has reverted to a single-particle hydrophobic state, while a small amount of LFP roasted particles that may be entrained remain hydrophilic. Through microbubble flotation treatment, microbubbles can selectively collide with and adhere to the hydrophobic NCM particles and carry them to the foam layer, while the hydrophilic LFP roasted particles remain in the slurry. This further removes the LFP roasted products entrained in the NCM product, which is beneficial for improving the purity of the NCM product. Simultaneously, since the chemical depolymerization step retains the hydrophobic adsorption layer on the surface of the NCM particles, the microbubble flotation step can be carried out directly without the need to add collectors again, which simplifies the operation and reduces reagent consumption.

[0047] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0048] Example 1:

[0049] A method for separating NCM and LFP from an NCM / LFP mixed black powder, comprising the following steps:

[0050] Step 1: Retired lithium iron phosphate (LFP) and lithium nickel cobalt manganese oxide (NCM) hybrid batteries were discharged (immersed in 5wt% NaCl solution for 24 h), mechanically disassembled, sheared and crushed (output particle size <5 mm), and vibrating sieve (200 mesh standard sieve) to obtain NCM / LFP mixed black powder. ICP-OES analysis showed that the mass ratio of LFP to NCM in this mixed black powder was 1:1. The black powder was placed in a forced-air drying oven and dried at 105℃ for 12 h to constant weight, then cooled in a desiccator for later use.

[0051] Step 2: Oxidative calcination of the NCM / LFP mixed black powder to convert LFP into calcined LFP particles. Specifically: Weigh 500 g of the dried mixed black powder and spread it evenly in a ceramic boat, with a layer thickness of approximately 10 mm. Place the ceramic boat in a programmable muffle furnace and heat it from room temperature to 500 ℃ at a rate of 8 ℃ / min. After reaching the target temperature, hold it at that temperature for 120 min. Air is introduced throughout the calcination process (flow rate 2 L / min) to maintain an oxidizing atmosphere inside the furnace. After calcination, turn off the heating power and allow the sample to cool naturally to room temperature with the furnace. Remove the calcined product, weigh it, and record the weight.

[0052] Step 3: Hydrophobize the NCM particles in the NCM / LFP mixed black powder. Specifically: Take 200 g of the whole roasted product obtained in Step 2, add 800 mL of deionized water, place it in a 2 L mixing tank (solid content 20%), turn on the stirrer, and stir at 400 rpm for 10 min to uniformly disperse the slurry; at this time, the initial pH of the slurry is measured to be 10.2 (because Li3Fe2(PO4)3 in the roasted product is alkaline due to hydrolysis); add dilute sulfuric acid (8% by volume) dropwise with a peristaltic pump, controlling the dropwise rate at 5 mL / min, while continuously monitoring the pH change of the slurry with a pH meter; when the pH drops to 8.5, stop adding acid, and continue stirring for 3 min until the pH stabilizes; if the pH fluctuates <0.05 within 3 min, it is considered to have reached equilibrium; record the final pH = 8.5. After the pH stabilizes, maintain the stirring speed of 400 rpm, and add the following reagents in sequence (the amount of each reagent is relative to the dry weight of the black powder): weigh modified starch (degree of substitution 0.3, average molecular weight about 8 × 10⁻⁶). 50.044 g of Da (i.e., 220 g / t) was added to 10 mL of deionized water and gelatinized in an 80 ℃ water bath for 15 min. After cooling to room temperature, it was added to the slurry and stirred for another 5 min. 0.040 g of benzohydroxyxamic acid (98% purity) (i.e., 200 g / t) was weighed and added to 5 mL of deionized water. One drop of NaOH solution (1 mol / L) was added to promote dissolution. After complete dissolution, it was added to the slurry and stirred for another 5 min.

[0053] Step 4: Aggregate NCM particles. Specifically, after the reagents from Step 3 have taken effect, add 2.0 g (1000 g / t) of emulsified kerosene to the slurry mixing tank. This emulsified kerosene is pre-emulsified using a Span-80 / Tween-80 composite emulsifier (HLB value = 10). Start the high-shear disperser (IKA T-25, rotor diameter 20 mm, stator-rotor clearance 0.5 mm), set the rotor linear velocity to 20 m / s (corresponding to a speed of approximately 19100 rpm), and start timing. The processing time is 8 minutes. During the processing, the slurry temperature rises by approximately 5-8℃, and the slurry temperature is maintained below 35℃ using circulating cooling water.

[0054] Step 5: Classify the NCM agglomerates and LFP roasted particles using the particle size difference. Specifically: Transfer all the agglomerated slurry (approximately 2 L) into a stirred storage tank, and pump it to a small hydrocyclone (12° cone angle, 10 mm overflow diameter, 5 mm underflow diameter) using a peristaltic pump. The feed pressure is controlled at 0.15 MPa (adjusted by the peristaltic pump speed and reflux valve). Collect the overflow and underflow products separately, with approximately 1.6 L of overflow and approximately 0.4 L of underflow. Filter, dry, and weigh both separately; the overflow product is the LFP roasted particles.

[0055] Step 6: Chemical depolymerization of NCM aggregates. Specifically: Transfer the underflow product (NCM aggregates, approximately 35 g wet weight and 18 g dry weight) into a 500 mL depolymerization tank, add deionized water to a final volume of 300 mL, add 0.030 g of 2-octanol (i.e., 150 g / t), turn on the stirrer, and stir at 150 rpm for 15 min.

[0056] Step 7: Perform flotation treatment on the deagglomerated MCN particles. Specifically: Transfer the deagglomerated slurry to a microbubble flotation column (column height 1.5 m, inner diameter 5 cm, microbubble generator model FZ-1), turn on the aeration (air) at a rate of 0.3 L / min, and skim the bubbles for 5 min. Collect the froth product (NCM concentrate) and the product in the tank (tailings) separately, filter, dry, and weigh.

[0057] Example 2-22:

[0058] NCM and LFP were separated from the NCM / LFP mixed black powder using a method essentially the same as in Example 1. Please refer to Table 1 for the distinguishing conditions.

[0059] Example 23:

[0060] The difference from Example 1 is that the sixth step is changed to physical depolymerization (without demulsifier): treatment at low shear conditions of 10 m / s for 8 min.

[0061] Example 24:

[0062] The difference from Example 1 is that the sixth step is changed to physical depolymerization (without demulsifier): treatment under high shear conditions of 20 m / s for 8 min.

[0063] Table 1 Comparison of conditions for the separation methods in Examples 1-22 of this application

[0064]

[0065] Comparative Example 1: A method for separating NCM and LFP from NCM / LFP mixed black powder, comprising the following steps: obtaining NCM / LFP mixed black powder according to the first step of Example 1, and then directly classifying the mixed black powder according to the fifth step of Example 1 to collect the overflow and underflow products.

[0066] Comparative Example 2: The difference from Example 1 is that the second step of oxidation calcination is not performed.

[0067] Comparative Example 3: The difference from Example 1 is that in the third step, after the pH stabilizes, the system is acidic, with pH=6.5.

[0068] Comparative Example 4: The difference from Example 1 is that, in the third step, after the pH stabilizes, the modified starch is removed from the added reagent.

[0069] Comparative Example 5: The difference from Example 1 is that in the third step, after the pH stabilizes, benzohydroxyxamic acid is removed from the added reagent.

[0070] Comparative Example 6: The difference from Example 1 is that in the third step, after the pH stabilizes, the reagents are added simultaneously, namely, modified starch and benzohydroxyxamic acid are added at the same time.

[0071] Comparative Example 7: The difference from Example 1 is that in the third step, after the pH stabilizes, the order of adding the reagents is reversed, that is, benzohydroxyxamic acid is added first, and then modified starch is added.

[0072] Comparative Example 8: The difference from Example 1 is that the fourth step is omitted. That is, after the NCM particles in the NCM / LFP mixed black powder are hydrophobized in the third step, the fifth step of classification is performed directly.

[0073] Comparative Example 9: The difference from Example 1 is that in the third step, after the pH stabilizes, the added reagent replaces benzohydroxyxamic acid with an equal amount of sodium oleate.

[0074] The testing method for this application is as follows:

[0075] 1. NCM grade determination (ICP-OES): Take 0.5 g of the flotation-treated foam product and place it in a polytetrafluoroethylene digestion vessel. Add 10 mL of aqua regia (HCl:HNO3 = 3:1, volume ratio) and digest in a microwave digester (180℃, 20 min). After digestion, transfer to a 50 mL volumetric flask and dilute to volume. Determine the Ni, Co, and Mn contents using ICP-OES (Agilent 5110), and calculate the NCM grade according to the NCM stoichiometry.

[0076] 2. NCM recovery rate = (NCM mass in underflow / total NCM mass in feed) × 100%.

[0077] 3. LFP product entrainment rate (XRD-Rietveld + chemical leaching verification): 0.5 g of the flotation product was taken, and the total content of Li3Fe2(PO4)3 and Fe2O3 was quantitatively analyzed using the XRD-Rietveld full-spectrum fitting method. Simultaneously, a chemical leaching verification method was used: another 0.5 g sample was taken, and 20 mL of 2 mol / L HCl solution was added. The mixture was then leached in a 60℃ water bath for 30 min to ensure complete dissolution of the LFP calcined product. After filtration, the filtrate was collected, and the Fe content was determined using the o-phenanthroline spectrophotometric method (λ=510 nm). 3+ The concentration, based on Fe 3+ The total amount was converted to LFP roasting product content. The difference between the two methods was less than 2%, so the average value was taken.

[0078] 4. Agglomerate particle size: This refers to the size of oil bridge agglomerates (secondary agglomerates) formed by NCM particles and emulsified oil droplets. Take 10 mL of the sample obtained after agglomeration treatment, place it on a glass slide, cover it with a coverslip, and observe and photograph the agglomerate morphology under an optical microscope (Olympus BX53, magnification 100×~400×). Use Image-Pro Plus image analysis software to statistically analyze the agglomerate particle size distribution. Count ≥200 agglomerates for each sample and measure the average agglomerate particle size.

[0079] 5. BHA Retention Rate (FTIR Peak Area Method): This refers to the percentage of benzo[a]hydroxyxamic acid (BHA) retained on the surface of NCM particles before and after depolymerization. Take 5 mg of NCM samples before and after depolymerization, mix with 200 mg of KBr, grind, and compress into tablets. FTIR-ATR (PerkinElmer Spectrum 100, ZnSe crystals, 4 cm⁻¹ resolution) is used. -1 Spectra were acquired by scanning 32 times. The peak of the C=O stretching vibration of BHA (1630 cm⁻¹) was used as the reference. -1 Peak area A1630 and NCM lattice vibration peak (550 cm⁻¹) -1 ) Calculation of the ratio of peak area A550: BHA retention rate = (A1630 / A550 after depolymerization) / (A1630 / A550 before depolymerization) × 100%.

[0080] 6. Selectivity coefficient β: An index used to measure the selective separation ability of a separation method for two minerals (NCM and LFP roasted products). Where C represents the grade or content of each product. β > 1: Selectivity is indicated; the larger the value, the more thoroughly NCM and LFP are separated.

[0081] Table 2. Test results of the separation effect of the separation methods in Examples 1-24 and Comparative Examples 1-9 of this application.

[0082]

[0083] Referring to Tables 1 and 2, in Examples 1-24 of this application, the mixed black powder is first oxidized and calcined to convert LFP into LFP calcined particles, establishing a difference in surface chemical properties between the LFP calcined particles and NCM particles. Subsequently, modified starch (or dextrin) and benzoyl hydroxamic acid are added sequentially under alkaline conditions. The modified starch selectively adsorbs onto the surface of the LFP calcined particles, inhibiting their adsorption, while benzoyl hydroxamic acid hydrophobizes the surface of the NCM particles through chelation. Next, emulsified oil is added under mechanical shearing, causing the hydrophobic NCM particles to selectively aggregate through oil bridging, forming micron-sized NCM aggregates, creating a particle size difference between them and the unaggregated LFP calcined particles. Finally, this particle size difference is used to separate the NCM aggregates from the LFP calcined particles through grading. As shown in Table 2, the NCM grade in the separation products obtained by the separation methods in Examples 1-24 of this application is 62.8%~95.3%, the NCM recovery rate is 52.7%~90.2%, and the selectivity coefficient β is 3.5~13.1. The NCM grade and recovery rate are both at a high level, and the LFP entrainment rate is low. This indicates that the steps in Examples 1-24 of this application, which involve creating surface chemical differences through oxidative roasting, selectively establishing hydrophobic differences through inhibitors and collectors, amplifying the agglomeration of emulsified oil into particle size differences, and fractional separation, solve the technical problem that it is difficult to selectively separate two fine particle mixtures with similar surface properties, LFP and NCM, through physical methods.

[0084] In Example 1, based on Examples 13-15, the calcination temperature was further controlled within the range of 480℃ to 550℃ and the calcination time was controlled within the range of 90 min to 150 min. The NCM grade, recovery rate and selectivity coefficient β were all improved, indicating that further controlling the calcination temperature and time within the above range helps to ensure the full conversion of LFP to LFP calcined particles to obtain sufficient surface chemical differences.

[0085] Based on Examples 16-17, Example 1 further controlled the ratio of LFP to NCM in the NCM / LFP mixed black powder within the range of 1:0.5 to 1:2. The NCM grade, recovery rate, and selectivity coefficient β were all improved, indicating that the separation method provided in this application has a better separation effect on the mixed black powder with the above ratio. With a fixed amount of starch and benzohydroxyxamic acid, they can fully act on their respective target particles.

[0086] Based on Example 18, Example 1 further controlled the pH of the alkaline conditions within the range of 8.0 to 9.0. The NCM grade, recovery rate, and selectivity coefficient β were all improved. This further illustrates that controlling the pH within the above range helps to achieve a balance between sufficient negative charge on the surface of LFP roasted particles to enable effective starch adsorption inhibition and sufficient metal active sites on the surface of NCM particles to allow for BHA chelation and capture. This reduces the risk that the negative charge on the surface of NCM particles is too strong at higher pH, which weakens the chelation and adsorption effect of BHA.

[0087] Based on Examples 19-20, Example 1 further controlled the modified starch dosage within the range of 150 g / t to 300 g / t and the benzohydroxyxamic acid dosage within the range of 150 g / t to 250 g / t. The NCM grade, recovery rate, and selectivity coefficient β were all improved, indicating that further controlling the starch dosage within the above range helps to form a complete but not excessive inhibition layer on the surface of LFP calcined particles, thereby reducing the amount of LFP entrained. Furthermore, further controlling the BHA dosage within the above range helps to form a sufficiently dense hydrophobic adsorption layer on the surface of NCM particles, thereby improving the aggregation efficiency.

[0088] Based on Examples 21-22, Example 1 further controlled the linear velocity of mechanical shearing within the range of 15 m / s to 25 m / s. The agglomerate particle size changed from 45 μm (lower linear velocity) and broken state (higher linear velocity) to complete agglomerates of 255 μm. The NCM recovery rate was improved, indicating that further controlling the linear velocity of mechanical shearing within the above range helps to obtain a moderate shear force field in the slurry, ensuring the uniform dispersion of emulsified oil droplets and sufficient collision and agglomeration between hydrophobic NCM particles to form NCM agglomerates with suitable particle size. At the same time, it also helps to reduce the risk of insufficient agglomeration when the linear velocity is low or the risk of agglomeration disintegration due to shear force tearing the formed oil bridge structure when the linear velocity is high.

[0089] Based on Examples 23-24, Example 1 further used a short-chain alcohol (2-octanol) with 3-8 carbon atoms as a demulsifier to replace physical depolymerization with chemical depolymerization. Both the BHA retention rate and NCM grade were improved, indicating that using a short-chain alcohol demulsifier for chemical depolymerization helps to gently disintegrate the oil bridge by reducing the oil-water interfacial tension, reducing the mechanical damage to the particle crystal structure and surface BHA adsorption layer caused by high-shear physical depolymerization, and allowing a higher proportion of collector to be retained on the surface of the depolymerized NCM particles, thereby obtaining a higher NCM grade and recovery rate in subsequent microbubble flotation treatment.

[0090] Compared to Example 1 of this application, Comparative Example 1 directly subjected the original NCM / LFP mixed black powder to cyclone classification. Since the LFP and NCM in the untreated mixed black powder are both micron-sized particles with overlapping particle size distributions, the grade of NCM in the classification product was only 35.2%, the recovery rate was only 48.5%, and the LFP entrainment rate was high. This indicates that the mixed black powder that has not been treated by the method of this application does not have physical property differences that can be effectively classified.

[0091] Compared to Example 1 of this application, Comparative Example 2 did not use the oxidative roasting step. Although it underwent reagent addition and agglomeration treatment, since LFP was not roasted and transformed, its original surface chemical properties were not significantly different from NCM. Starch could not selectively adsorb and inhibit LFP, and the NCM grade was only 45.3%. This indicates that oxidative roasting is one of the key conditions for creating the surface chemical difference between LFP and NCM and making subsequent selective inhibition possible.

[0092] Compared to Example 1 of this application, Comparative Example 3 was hydrophobized under acidic conditions. At this time, the surface negative charge of the LFP calcined particles was insufficient, and starch could not be effectively adsorbed and inhibited. The selectivity was poor, with NCM grade of only 55.6% and β value of only 2.8. This shows the necessity of maintaining the separation system under alkaline conditions (pH 8.0~9.0) to exert an inhibitory effect on starch.

[0093] Compared to Example 1 of this application, Comparative Example 4 removed modified starch in the hydrophobic treatment step. Due to the lack of starch inhibitor, benzohydroxyxamic acid was adsorbed on both the LFP calcined particles and NCM particles. The NCM grade was only 51.2% and the β value was only 1.8 (close to non-selectivity). The LFP entrainment rate was high, indicating that starch as an LFP inhibitor is one of the key conditions for achieving selective separation.

[0094] Compared to Example 1 of this application, Comparative Example 5, which eliminates benzohydroxyxamic acid, cannot hydrophobize NCM due to the lack of a collector, and the emulsified oil cannot agglomerate. Most of the NCM particles are lost with the overflow, and the NCM recovery rate is only 12.5%, indicating that benzohydroxyxamic acid is one of the key conditions for achieving selective hydrophobization of NCM.

[0095] Compared to Example 1 of this application, Comparative Example 6 adds modified starch and benzoyl hydroxamic acid simultaneously, which does not meet the preset order of reagent addition. This is because the Fe on the surface of the BHA and LFP calcined particles... 3+BHA has a stronger binding affinity than starch, preferentially occupying the active sites on the LFP surface. Starch cannot replace the adsorption sites already occupied by BHA, leading to a significant decrease in selectivity, with an NCM content of only 61.2% and a β value of only 3.2. Comparative Example 7, which reversed the reagent addition order to BHA followed by starch, also did not meet the preset reagent addition order. In this case, BHA occupied the active sites on the surface of the calcined LFP particles first, resulting in starch's inability to effectively inhibit the reaction, with an NCM content of only 58.9% and a β value of only 2.8. Comparative Examples 6 and 7 collectively demonstrate that the preset reagent addition order (adding modified starch first, then benzoyl hydroxamic acid) is one of the key conditions for achieving selective separation.

[0096] Compared to Example 1 of this application, Comparative Example 8 did not use emulsified oil agglomeration treatment. The NCM particles after hydrophobization still existed in a fine particle state (<74 μm), and there was a lack of sufficient particle size difference between them and the LFP calcined particles. The cyclone classification could not effectively cut them, and the NCM grade was only 52.4% and the recovery rate was only 45.6%. This shows that emulsified oil agglomeration is one of the key conditions for converting surface chemical differences into separable physical differences (particle size differences).

[0097] Compared to Example 1 of this application, Comparative Example 9, which uses sodium oleate instead of benzohydroxyxamic acid as the collector, has an NCM grade of only 52.3%, a recovery rate of only 58.6%, and a selectivity coefficient β of only 2.5, which are significantly lower than the 95.3%, 90.2%, and 13.1% of Example 1. This indicates that the selective collection ability of sodium oleate as a fatty acid collector for NCM is far inferior to that of benzohydroxyxamic acid. This is because benzohydroxyxamic acid is a chelating collector, and its hydroxyxamic group can form stable five-membered ring chelates with transition metal ions such as Ni, Co, and Mn on the surface of NCM particles, exhibiting high chemical selectivity. Sodium oleate, on the other hand, mainly acts on the particle surface through physical adsorption or chemical adsorption, and has limited ability to distinguish between LFP roasted particles and NCM particles.

[0098] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for separating NCM and LFP from an NCM / LFP mixed black powder, characterized in that, Includes the following steps: The mixed black powder is oxidized and calcined to convert LFP into LFP calcined particles; In the mixed black powder after oxidative roasting, LFP inhibitor and NCM collector are added sequentially, and under alkaline conditions, the NCM particles are hydrophobized independently of the LFP roasted particles. Adding emulsified oil causes the hydrophobic NCM particles to agglomerate under mechanical shearing, forming NCM agglomerates. The NCM agglomerates and the LFP calcined particles have a particle size difference. The NCM aggregates and LFP calcined particles are classified using the particle size difference to prepare mutually separated NCM and LFP.

2. The method as described in claim 1, characterized in that, The oxidation calcination temperature is 480℃~550℃, and the time is 90 min~150 min.

3. The method as described in claim 1, characterized in that, The method satisfies at least one of the following conditions: (1) The pH of the alkaline conditions is 8.0~9.0; (2) The LFP inhibitor includes modified starch and / or dextrin; (3) The NCM collector includes one or more of benzohydroxyxamic acid, salicylic acid, phthalic acid, octylhydroxyxamic acid and isobutylhydroxyxamic acid.

4. The method as described in claim 3, characterized in that, The method also satisfies at least one of the following conditions: (1) Based on the dry weight of the mixed black powder, the dosage of the LFP inhibitor is 150 g / t to 300 g / t; (2) Based on the dry weight of the mixed black powder, the amount of NCM collector used is 150 g / t to 250 g / t.

5. The method as described in claim 1, characterized in that, The method also satisfies at least one of the following conditions: (1) Based on the dry weight of the mixed black powder, the amount of emulsified oil used is 500 g / t to 1500 g / t; (2) The linear velocity of the mechanical shearing is 15 m / s to 25 m / s, and the processing time is 5 min to 10 min.

6. The method as described in claim 5, characterized in that, The emulsified oil includes one or more of kerosene, diesel oil, paraffin oil, light white oil, naphthenic oil, and transformer oil.

7. The method as described in claim 1, characterized in that, After the classification, the NCM aggregates are collected as underflow products and the LFP calcined particles are collected as overflow products.

8. The method as described in claim 1, characterized in that, After separating the NCM aggregates from the LFP calcined particles based on their hydrophobicity difference, the method further includes: The separated NCM aggregates were chemically depolymerized under the action of a demulsifier.

9. The method as described in claim 8, characterized in that, The demulsifier satisfies at least one of the following conditions: (1) The demulsifier includes short-chain alcohols, wherein the number of carbon atoms in the short-chain alcohols is 3 to 8; (2) Based on the dry weight of the mixed black powder, the amount of the demulsifier is 100 g / t to 200 g / t.

10. The method as described in claim 8, characterized in that, The method further includes: performing microbubble flotation treatment on the chemically depolymerized slurry.

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