Medicament group for separating carbon-coated lithium iron phosphate from graphite by flotation and application thereof

Abstract

The application discloses a medicament group for floatation separation of carbon-coated lithium iron phosphate and graphite and application thereof, and belongs to the technical field of resource utilization of waste batteries. The medicament group comprises a collector, a foaming agent and an inhibitor. The collector is at least one of n-dodecane, kerosene and diesel oil. The foaming agent is at least one of methyl isobutyl carbinol and terpineol. The inhibitor is at least one of carboxymethyl cellulose and sodium sulfite. The medicament group designed in the application is used in recycling of positive and negative electrode materials of lithium iron phosphate batteries, and carbon-coated lithium iron phosphate and graphite electrode materials can be efficiently separated through floatation separation. The application has the advantages of simple process, high separation efficiency, economy and environmental protection, and solves the problems that the positive electrode is carbon-coated lithium iron phosphate, the positive electrode and the negative electrode are mixed together, the traditional medicament cannot separate the positive and negative electrode materials, and the loss rate of the positive electrode material powder is high during the separation process.

Description

TECHNICAL FIELD

[0001] The application discloses a medicament group for separating carbon-coated lithium iron phosphate from graphite by flotation and application, and relates to the technical field of resource utilization of waste batteries. BACKGROUND

[0002] Lithium iron phosphate batteries have been widely used in the field of new energy vehicles in recent years due to their high energy density and working voltage, long cycle life, low self-discharge rate, environmental friendliness and other advantages. With the wide application and development of lithium batteries, the prices of raw ore resources of some energy metals, phosphorus chemical industry and fluorine chemical industry have risen sharply. Therefore, efficient separation and recycling of valuable substances in waste lithium batteries have become a major technical problem faced by technology workers. Improper disposal of waste lithium batteries can also cause serious environmental problems, and harmless treatment and efficient recycling of waste lithium batteries have become a real problem faced by the development of national economy and social progress.

[0003] At present, in the recycling and treatment of waste lithium iron phosphate batteries, coarse particles (such as plastic shells, diaphragms, copper foils, aluminum foils, etc.) can be separated by magnetic separation, gravity separation and other methods, and after a series of pretreatments (such as discharging, disassembling and crushing, etc.), they are separated according to the differences in physical properties. Fine particle electrode powder (such as graphite, lithium iron phosphate, etc.) is mainly purified by hydrometallurgy and pyrometallurgy. However, both hydrometallurgy and pyrometallurgy have some problems, such as high processing cost, complex process, serious environmental pollution, and most of the valuable elements have not been effectively and economically recovered.

[0004] Flotation is a physical separation method based on the difference in particle surface wettability. At present, lithium battery recycling, lithium cobaltate battery is hydrophilic due to the hydrophilic surface of lithium cobaltate, and the hydrophobic surface of graphite, and the difference between the two is large, so the positive and negative materials can be separated by flotation, in 201710392010.8, the reagent system used is collector kerosene, the dosage is 200g / t, the frother is pine oil, the dosage is 200g / t, the graphite content is 83.67%, the recovery rate of graphite tailings is 75.88%, and the lithium cobaltate content is 93.56%, the recovery rate of lithium cobaltate concentrate is 59.38%; Compared with lithium cobaltate battery flotation, the biggest difficulty in lithium iron phosphate battery flotation is that the surface of lithium iron phosphate electrode material is coated with a layer of amorphous carbon, and the difference between the two is small, and the surface of the graphite electrode material is modified into spherical graphite, which is difficult to separate using traditional reagents, and is not as easy to separate as lithium cobaltate and graphite electrode material. At present, 202310520043.1 uses flotation method to treat lithium iron phosphate positive material in waste lithium iron phosphate battery, and the reagent group adopts polyvinylpyrrolidone (PVP) 25g / t + polyacrylic acid (PAA) 250g / t, collector kerosene 300g / t, frother methyl isobutyl carbinol (MIBC) 100-200g / t, which can recover positive material LiFePO4 with content of 71.95% and recovery rate of 83.59%, and negative material graphite with content of 88.36% and recovery rate of 79.27%, but the reagents used are relatively difficult to degrade, and contain 3 types of carcinogens, which have greater environmental risk; At the same time, the mutual content of lithium iron phosphate and graphite in flotation concentrate product is high.

[0005] For the flotation separation of lithium iron phosphate battery positive and negative mixed materials, there are generally problems such as that the positive electrode is carbon-coated lithium iron phosphate, which leads to the difficulty in separating the positive and negative materials using traditional reagents after mixing with the negative electrode, and the high loss rate of positive electrode material in the separation process. Therefore, it is of great significance to develop more economical, efficient and green reagent groups for flotation separation of carbon-coated lithium iron phosphate and graphite. SUMMARY

[0006] The present application aims to provide a flotation reagent group for separating lithium iron phosphate and its application, to solve the problems of difficult separation of positive and negative materials in waste lithium iron phosphate battery and high loss rate of positive material in the separation process, especially to solve the problem of high loss rate of positive and negative materials in the comprehensive recovery and separation of carbon-coated lithium iron phosphate waste lithium battery.

[0007] Due to the carbon-coated lithium iron phosphate positive electrode, it is difficult to achieve efficient separation by using ordinary process after mixing with the negative electrode.

[0008] In order to solve the above technical problems, the present application provides a medicament group for floatation separation of carbon-coated lithium iron phosphate and graphite and application thereof; the medicament group comprises a collector, a frother and an inhibitor; the medicament group is used for floatation separation of carbon-coated lithium iron phosphate and graphite; the collector is selected from at least one of n-dodecane, kerosene and diesel oil;

[0009] The frother is selected from at least one of MIBC (methyl isobutyl carbinol) and terpineol;

[0010] The inhibitor is at least one of CMC (carboxymethyl cellulose) and sodium sulfite;

[0011] As a preferred scheme, the present application provides a medicament group for floatation separation of carbon-coated lithium iron phosphate and graphite and application thereof; the collector is selected from at least one of n-dodecane, kerosene and diesel oil, and preferably n-dodecane;

[0012] The frother is selected from at least one of MIBC and terpineol, and preferably MIBC;

[0013] The inhibitor is at least one of CMC and sodium sulfite; the molecular weight of the CMC ranges from 8000 to 16000, the degree of substitution ranges from 0.1 to 0.3, the carboxymethyl cellulose has a viscosity ranging from 10 to 1000 mPa·s when 2wt% is dissolved in water at 25°C, and the viscosity is preferably 10 to 200 mPa·s, and the viscosity is further preferably 25 to 200 mPa·s.

[0014] As a preferred scheme, the amount of the collector ranges from 5 g / t to 20 g / t.

[0015] As a preferred scheme, the amount of the frother ranges from 5 g / t to 20 g / t.

[0016] As a preferred scheme, the amount of the inhibitor ranges from 50 g / t to 1000 g / t.

[0017] The ratio of the CMC to the sodium sulfite ranges from 1:5 to 1:12, and preferably from 1:8 to 1:10.

[0018] In the technical development process of the present application, ordinary frothers and inhibitors are used, kerosene and diesel oil are used as collectors, and the collectors are used for floatation separation of lithium iron phosphate battery electrode materials, but the separation effects are not ideal, and in many cases, the froth mineralization is poor and the froth is seriously mixed and interwoven.

[0019] In the technical development process of the present application, according to the analysis of the inhibition effect of CMC adsorbed on the surface of the mineral, it is found through experiments that carboxymethyl cellulose can realize selective inhibition of both, and the results of experimental verification find that low viscosity CMC (viscosity of 25-200 mPa·s) has better inhibition effect on lithium iron phosphate. The amount of the inhibitor is usually low, which is 100-300 g / t. At the same time, it is also found that when the high viscosity CMC (i.e. the viscosity is greater than 200 mPa·s), there are problems of poor selectivity and weak dispersion.

[0020] As a preferred solution, the application of a reagent group for flotation separation of carbon-coated lithium iron phosphate and graphite; the application comprises: using the reagent group in the flotation process to separate the carbon-coated lithium iron phosphate and graphite raw materials in the treatment object by flotation, and the particle size of the treatment object is 85%-90% of the total particle mass.

[0021] As a preferred solution, the application of a reagent group for flotation separation of carbon-coated lithium iron phosphate and graphite; characterized in that;

[0022] The application comprises the following steps:

[0023] Step A

[0024] The treatment object is mixed with water to prepare a mixed slurry;

[0025] Step B

[0026] The inhibitor, collector and frother in the reagent group are added to the mixed slurry to separate the carbon-coated lithium iron phosphate and graphite by flotation, and the flotation obtains the concentrate and the tailings;

[0027] The collector is selected from at least one of n-dodecane, kerosene and diesel;

[0028] The frother is selected from at least one of MIBC and terpineol;

[0029] The inhibitor is at least one of CMC and sodium sulfite.

[0030] As a preferred solution, the application of a reagent group for flotation separation of carbon-coated lithium iron phosphate and graphite and its application; the treatment object is preferably carbon-coated lithium iron phosphate and graphite for battery preparation.

[0031] As a preferred solution, the application of a reagent group for flotation separation of carbon-coated lithium iron phosphate and graphite and its application; in step B, the pH of the slurry is controlled to be 8-9.5 during flotation;

[0032] The amount of the inhibitor is controlled in the range of 50 g / t-1000 g / t, and preferably in the range of 100 g / t-300 g / t;

[0033] The ratio of CMC to sodium sulfite is controlled in the range of 1:5 to 1:12, preferably 1:8 to 1:10;

[0034] The amount of the collector is controlled in the range of 5 g / t to 20 g / t, preferably 10 to 15 g / t;

[0035] The amount of the frother is controlled in the range of 5 g / t to 20 g / t, preferably 6 to 9 g / t;

[0036] The preferred amount of the depressant is 100 to 300 g / t. In the mixed electrode material flotation experiment, when the amount of CMC is 150 g / t, the content of lithium iron phosphate in the tailings is 79.06%, and the recovery rate is 82.71%.

[0037] When the collector is n-dodecane, the amount is 15.0 g / t, the frother is MIBC, the amount is 7.5 g / t, the pulp pH is controlled at 9.3±0.1, the flotation time is 3 min, the depressant is CMC, and the amount is 150 g / t, after flotation, the content of lithium iron phosphate in the flotation tailings is greater than 79%, and the recovery rate is greater than 82.5%.

[0038] When the collector is n-dodecane, the amount is 15.0 g / t, the frother is MIBC, the amount is 7.5 g / t, the pulp pH is controlled at 9.3±0.1, the flotation time is 3 min, the depressant is CMC+Na2SO3 combination, the amount of CMC is 25 g / t, and the amount of Na2SO3 is 250 g / t, after flotation, the content of graphite in the concentrate is greater than 96%, and the recovery rate of lithium iron phosphate in the tailings is greater than 98%.

[0039] The concentrate obtained by flotation is graphite, and the tailings are carbon-coated lithium iron phosphate. By using the reagent group of the present application for flotation separation, carbon-coated lithium iron phosphate and graphite electrode material can be efficiently separated, which has the advantages of simple process, high separation efficiency, economic and environmental protection, and solves the problems that the positive electrode is carbon-coated lithium iron phosphate, which leads to the difficulty in separating the positive electrode from the negative electrode by using traditional reagents, and the high loss rate of positive electrode material powder in the separation process.

[0040] When the reagent group designed by the present application is used for flotation separation of carbon-coated lithium iron phosphate and graphite raw materials, the amount of the collector n-dodecane is very small, and most of it is adsorbed on the surface of the particles, which causes little water pollution. At the same time, the depressant carboxymethyl cellulose involved in the present application has a low amount, and polysaccharides are biodegradable, so the scheme of the present application has the advantages of environmental protection and sustainable application; at the same time, the separation effect and the recovery rate of each material are very high, which has obvious industrial application value.

[0041] Principle and innovation

[0042] During the research process of this invention, it was discovered that after waste lithium iron phosphate batteries are crushed and screened, the lithium iron phosphate and graphite electrode active materials usually exist in the form of fine particles. Laser particle size analysis was used to analyze the particle size composition of the lithium iron phosphate and graphite electrode active materials, and the results are shown in the appendix. Figure 1 The study found that the average volumetric particle size of most graphite samples was concentrated in the range of 10–30 μm, with the graphite sample having a volumetric average particle size of 23.826 μm. In contrast, the LFP sample had a volumetric average particle size of 3.524 μm. LFP exhibited a non-uniform distribution, divided into two main particle size components due to agglomeration: an extremely fine portion of 3–5 μm and a coarser portion of 100–400 μm. Based on TEM analysis of the surface morphology of the two electrode active materials, lithium iron phosphate particles were found to be encapsulated by a transparent carbon matrix; that is, the lithium iron phosphate aggregates consisted of LiFePO4 particles and a carbon coating layer. Graphite exhibited a distinct layered structure, and the surface properties of both materials were similar, increasing the difficulty and precision requirements for flotation separation.

[0043] This invention addresses the flotation separation of carbon-coated lithium iron phosphate (LFP) and graphite samples used in battery manufacturing. It employs a polysaccharide inhibitor, carboxymethyl cellulose (CMC). The adsorption of CMC on mineral surfaces primarily involves electrostatic interactions, hydrogen bonding, hydrophobic association, and chemical bonding. Analysis suggests that the main adsorption mechanism of CMC on LFP surfaces is a combination of chemical adsorption and hydrogen bonding. Conversely, CMC weakly adsorbs onto graphite surfaces through physical adsorption. Therefore, CMC can selectively interact with LFP surfaces, amplifying the wettability difference between LFP and graphite, thus achieving selective flotation separation. Furthermore, the selective dispersing effect of CMC also improves flotation efficiency. During flotation, excessively coarse or fine particles cannot float. Low-viscosity CMC is a good dispersant for LFP, promoting the dispersion of coarse LFP particles. Simultaneously, it helps weaken heterogeneous aggregation between LFP and graphite, reducing the inclusion of fine LFP particles in trace amounts of graphite and the entrainment of LFP in foam, thereby improving the quality of the flotation concentrate.

[0044] Advantages

[0045] The separation of traditional fine graphite material and waste lithium iron phosphate (generally with a carbon coating layer) material powder needs to adopt hydrometallurgy and pyrometallurgy processes, which has disadvantages such as high processing cost, complex process, serious environmental pollution, and most of the valuable elements have not been effectively and economically recovered. In the present application, the flotation method is used to separate graphite material and lithium iron phosphate according to the difference in wettability of the surface of the material, which can improve the separation efficiency of the positive and negative electrode materials on the one hand, and can reduce the processing and recycling cost of the waste lithium iron phosphate battery on the other hand. In addition, the use of the reagent group of the present application solves the problem that the difference in hydrophobicity between the graphite material and the lithium iron phosphate material is small due to the surface modification of the graphite material into spherical graphite and the surface coating of the lithium iron phosphate material with an amorphous carbon layer, and the use of traditional reagents is difficult. At the same time, the CMC and sodium sulfite are compounded, and the appropriate ratio can be used as a promising combined inhibitor for the separation of carbon-coated lithium iron phosphate and graphite. At present, a part of high content graphite can be separated, which is beneficial to the subsequent graphite regeneration, and the graphite remaining in the tailings can also be recycled after the LFPs leaching is completed. This shows that the present application is a more suitable separation reagent system, which can realize efficient flotation separation of graphite and lithium iron phosphate electrode material under the premise of considering the production cost, and has the advantages of simple process, simple operation, high separation efficiency, economy and environmental protection. BRIEF DESCRIPTION OF DRAWINGS

[0046] FIG. 1 is a particle size distribution diagram of carbon-coated lithium iron phosphate and graphite electrode active materials; Figure 1

[0047] FIG. 4 is a flotation result diagram of different CMC and Na2SO3 ratio as an inhibitor in Example 6. Figure 2 DETAILED DESCRIPTION

[0048] In order to facilitate clear understanding of the technical scheme of the present application, the following will be described in detail in combination with examples.

[0049] The results in the examples and comparative examples are all the results of one flotation.

[0050] Example 1

[0051] In the laboratory electrode material flotation research process, different amounts of inhibitors were used for flotation experiments of graphite and carbon-coated lithium iron phosphate electrode materials, and the Gaudin selectivity index was calculated based on the best separation effect of the reagent to uniformize the separation effect. The larger the selectivity index, the better the flotation separation effect of the reagent used.

[0052] The Gaudin selectivity index calculation formula is:

[0053] ​​wherein εC-K represents the recovery rate of graphite in the concentrate, εC-X represents the recovery rate of graphite in the tailings, εLFPs-K represents the recovery rate of carbon-coated lithium iron phosphate in the concentrate, and εLFPs-X represents the recovery rate of carbon-coated lithium iron phosphate in the tailings.

[0054] In the flotation separation experiment, the electrode material was the carbon-coated LFPs and graphite raw material sample used for battery preparation, the collector was n-dodecane, the dosage was 10.0 g / t, the frother was MIBC, the dosage was 7.5 g / t, the pulp pH was controlled at 9.3±0.1, and the flotation time was 3 min.

[0055] When the inhibitor was sodium sulfite, the dosage of sodium sulfite was 250 g / t, the recovery rate of LFPs coated with a carbon layer in the flotation concentrate was 4.74%, the recovery rate of graphite was 94.48%, the recovery rates of LFPs and graphite in the tailings were 95.26% and 5.52% respectively, and the separation coefficient of the two reached a maximum value of 18.54.

[0056] Example 2

[0057] When the inhibitor was carboxymethyl cellulose (CMC), other conditions were consistent with those in Example 1, the carbon-coated LFPs were greatly affected by CMC, and when the dosage of CMC was 50 g / t, the recovery rate decreased from 28.57% without CMC to 5.42%, the recovery rate of graphite was 98.21%, the recovery rates of LFPs and graphite in the tailings were 94.58% and 1.79% respectively, and the selectivity index was 28.37. When the dosage of CMC was 1000 g / t, the recovery rate of LFPs was 2.12%, the recovery rate of graphite remained 93.01%, the recovery rates of LFPs and graphite in the tailings were 97.88% and 6.99% respectively, and the selectivity index was 30.1.

[0058] Comparative Example 2.1: other steps were consistent with those in Example 2, starch was used as the inhibitor, the dosage of starch was 50 g / t, the recovery rates of graphite and LFPs were 4.98% and 9.12% respectively, the recovery rates of graphite and LFPs in the tailings were 95.02% and 90.88% respectively, and the selectivity index of the two was 0.72.

[0059] Comparative Example 2.2: other steps were consistent with those in Example 2, dextrin was used as the inhibitor, the dosage of dextrin was 50 g / t, the recovery rates of graphite and LFPs were 6.26% and 15.70% respectively, the recovery rates of graphite and LFPs in the tailings were 93.74% and 84.30% respectively, and the selectivity index was 0.60.

[0060] Example 3

[0061] In the study of the inhibitory effect of CMC on LFPs and graphite, the concentration range of CMC was reduced to 100 g / t, and the other conditions were consistent with Example 1. When the dosage of CMC was 50 g / t, the recovery rates of graphite and LFPs in the flotation concentrate were 97.88% and 5.42%, respectively, and the recovery rates of graphite and LFPs in the tailings were 2.12% and 94.58%, respectively. The selectivity separation index reached a maximum value of 28.37.

[0062] It was found through Examples 1, 2, 3 and Comparative Examples 2.1, 2.2 that Na2SO3 had a good separation effect on LFPs and graphite. The three polysaccharide inhibitors used in the experiment all had an inhibitory effect on both graphite and LFPs. Among them, starch and dextrin had a very obvious inhibitory effect on LFPs and graphite, and could reduce the recovery rates of both to a low level at very low dosages, with poor separation effect. CMC showed a good separation effect in the flotation process of both. When the dosage of CMC was 50 g / t, the recovery rates of graphite and LFPs were 97.88% and 5.42%, respectively, and the recovery rates of graphite and LFPs in the tailings were 2.12% and 94.58%, respectively, providing a basis for realizing high-efficiency selective flotation separation of graphite and carbon-coated LFPs.

[0063] Example 4

[0064] In the laboratory electrode material flotation study, CMC with different viscosities was used to conduct flotation experiments on graphite and carbon-coated lithium iron phosphate electrode materials. In this flotation separation experiment, the electrode material was carbon-coated LFPs and graphite raw material samples for battery preparation, the collector was n-dodecane with a dosage of 15.0 g / t, the frother was MIBC with a dosage of 7.5 g / t, the pulp pH was controlled at 9.3±0.1, and the flotation time was 3 min.

[0065] When the dosage of CMC with a viscosity of 25 mPa·s was 100 g / t, the recovery rates of graphite and LFPs in the flotation concentrate were 96.37% and 3.47%, respectively, and the recovery rates of graphite and LFPs in the tailings were 3.63% and 96.53%, respectively.

[0066] Comparative Example 4.1: CMC with a viscosity of 75 mPa·s was used as the inhibitor, and the other steps were consistent with Example 4. The dosage of CMC was 100 g / t, the recovery rates of graphite and LFPs were 81.23% and 3.98%, respectively, and the recovery rates of graphite and LFPs in the tailings were 18.77% and 96.02%, respectively.

[0067] Comparative Example 4.2: The other steps were consistent with Example 4, and the viscosity of CMC was 1000 mPa-s, the dosage of CMC was 100 g / t, the recovery rate of graphite and LFPs was 48.34% and 4.78%, and the recovery rate of tailings graphite and LFPs was 51.66% and 95.22%, respectively.

[0068] It was found from Comparative Examples 4.1, 4.2 and Example 4 that low viscosity CMC (25 mPa-s) had excellent selectivity in separating graphite and LFPs.

[0069] Example 5

[0070] During the laboratory electrode material flotation study, different dosages of the depressant CMC were used for flotation experiments on graphite and carbon-coated lithium iron phosphate mixed electrode materials.

[0071] In this flotation separation experiment, the carbon-coated LFPs and graphite raw material samples for battery preparation were used, the ratio of LFPs and graphite was fixed at 1:1, the collector was n-dodecane, the dosage was 15.0 g / t, the frother was MIBC, the dosage was 7.5 g / t, the pulp pH was controlled at 9.3±0.1, the flotation time was 3 min, and the effect of CMC on the flotation separation of LFPs and graphite was investigated. The experimental results are shown in Table 3.

[0072] Table 3: Flotation experimental results of graphite and carbon-coated LFPs mixed electrode materials

[0073]

[0074] The content of carbon-coated lithium iron phosphate in the tailings was 79.06%, which was much higher than the prior art, and the recovery rate was 82.71%, and the selectivity index was 4.13.

[0075] Comparative Example 5.1: The other steps were consistent with Example 5, and the dosage of CMC was 50 g / t, the content of flotation concentrate graphite and LFPs was 61.76% and 38.24%, the recovery rate was 52.85% and 33.24%, and the selectivity index was 1.50.

[0076] Comparative Example 5.2: The other steps were consistent with Example 5, and the dosage of CMC was 300 g / t, the content of flotation concentrate graphite and LFPs was 85.76% and 14.24%, the recovery rate was 42.86% and 7.45%, and the selectivity index was 1.88.

[0077] It is found from Comparative Examples 5.1, 5.2 and Example 5 that the content and recovery rate of carbon-coated LFPs are both decreasing, and the content of graphite is rapidly increasing, and the recovery rate presents a trend of first decreasing and then increasing and then decreasing in the whole flotation range. This may be related to the dispersion effect of CMC. When the concentration of CMC is low, the dispersion effect is not strong, LFPs and graphite are aggregated together, and graphite is taken into the flotation tailings together with LFPs; when the concentration of CMC is high, the aggregates of LFPs and graphite are fully dispersed and dissociated, graphite is adhered to the bubble and floated to the froth concentrate, so the recovery rate increases. Continue to increase the concentration of CMC, the recovery rates of LFPs and graphite both present a decreasing trend. At this time, it shows that more LFPs and less graphite are inhibited under the condition of CMC, and the greater the concentration of CMC, the more significant the inhibition effect.

[0078] Example 6

[0079] In the laboratory electrode material flotation research process, different proportions of inhibitors CMC+Na2SO3 were used for flotation experiments of graphite and carbon-coated lithium iron phosphate mixed electrode materials, and other conditions were consistent with Example 5. The experimental results are shown in Table 6. Figure 2 .

[0080] When 25 g / t CMC+250 g / t Na2SO3 is used, the content of graphite and carbon-coated LFPs in the flotation concentrate can reach 96.88% and 3.12%, the recovery rate of LFPs in the flotation tailings can reach 98.99%, and the content is 59.06%, and the selectivity index is 6.70 at this time. This scheme can separate a part of high-content graphite on the one hand, which is beneficial to the subsequent regeneration of graphite, and on the other hand, it is beneficial to improve the recovery rate of lithium iron phosphate, but the content is not high, and can be re-flotation, and after adjusting the flotation agent, the further separation of graphite and carbon-coated lithium phosphate can be realized.

[0081] Comparative Example 6.1: other steps are consistent with Example 6, only sodium sulfite is used, and when the dosage is 250 g / t, the content of graphite and LFPs in the flotation concentrate is 58.82% and 41.18%, and the recovery rate is 40.12% and 27.75%; the content of graphite and LFPs in the flotation tailings is 45.44% and 54.57% respectively, and the recovery rate is 59.88% and 71.91% respectively, and the selectivity index is 1.31.

[0082] Comparative Example 6.2: other steps are consistent with Example 6, and when the dosage of CMC is 25 g / t, the content of graphite and LFPs in the flotation concentrate is 27.65% and 42.35%, and the recovery rate is 37.77% and 28.09%; the content of graphite and LFPs in the flotation tailings is 46.27% and 53.73% respectively, and the recovery rate is 62.23% and 72.25% respectively, and the selectivity index is 1.26.

[0083] Comparative Example 6.3: Other steps are consistent with Example 6, when 25 g / t CMC + 125 g / t Na2SO3 is used, the content of graphite and LFPs is 63.41% and 36.59%, the recovery rate is 31.84% and 18.37%; the content of graphite and LFPs in the flotation tailings is 45.5% and 54.5%, the recovery rate is 68.16% and 81.63%, and the selectivity index is 1.44.

[0084] It is found by Comparative Examples 6.1, 6.2, 6.3 and Example 6 that when the ratio of CMC to sodium sulfite is 1:10, the separation effect is better than that of the ratio 1:5 and the use of the inhibitors CMC and sodium sulfite alone, and a part of high content graphite can be sorted, which is beneficial to the subsequent graphite regeneration, and the graphite remaining in the tailings can be recycled after the LFPs leaching is completed, indicating that the combination of CMC and sodium sulfite with a suitable ratio can be used as a promising combined inhibitor for separating carbon-coated lithium iron phosphate and graphite.

[0085] It can be seen from Examples 1 to 6 and Comparative Examples that sodium sulfite, CMC and their combined inhibitors can be used as effective flotation inhibitors for separating carbon-coated LFPs and graphite. The reagent group and application for separating carbon-coated lithium iron phosphate and graphite by flotation provided by the present application can efficiently separate the positive and negative electrode materials in the waste lithium iron phosphate battery electrode powder by flotation, and the recovery rate of the positive electrode material lithium iron phosphate is high during the separation process, which can solve the problem of high loss rate of the positive electrode material.

[0086] Finally, it should be noted that: the above examples are only used to illustrate the technical scheme of the present application, which is simple in process, convenient in operation, high in recovery rate and has obvious industrial application value, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical scheme recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical scheme deviate from the spirit and scope of the technical scheme of the embodiments of the present application.

Claims

1. The use of a medicament composition for the floatation separation of carbon-coated lithium iron phosphate and graphite, characterized in that The method comprises the following steps: Step A Mixing the object to be treated with water to prepare a mixed slurry, the object to be treated comprising carbon-coated lithium iron phosphate for batteries and graphite; Step B Adding an inhibitor, a collector and a frother in the reagent group to the mixed slurry to separate the carbon-coated lithium iron phosphate and the graphite by flotation, and obtaining a concentrate and a tailing by flotation; The collector is selected from at least one of n-dodecane, kerosene and diesel oil; The frother is selected from at least one of methyl isobutyl carbinol and terpineol; The inhibitor is composed of carboxymethyl cellulose and sodium sulfite at a mass ratio of 1:5 to 1:12; the carboxymethyl cellulose has a viscosity of 10 to 200 mPa·s at 25°C when 2 wt.% is dissolved in water.

2. The application of the reagent group for separating carbon-coated lithium iron phosphate and graphite by flotation according to claim 1, characterized in that: The carboxymethyl cellulose has a molecular weight of 8000 to 16000 and a degree of substitution of 0.1 to 0.

3.

3. The use of a medicament composition for separating carbon-coated lithium iron phosphate from graphite according to claim 1, characterized in that: The carboxymethyl cellulose has a viscosity of 25 to 200 mPa·s.

4. The application of the reagent group for separating carbon-coated lithium iron phosphate and graphite by flotation according to claim 1, characterized in that: The amount of the collector is 5 g / t to 20 g / t; The amount of the frother is 5 g / t to 20 g / t; The amount of the inhibitor is 50 g / t to 1000 g / t; The ratio of the carboxymethyl cellulose to the sodium sulfite is 1:2 to 1:

12.

5. The use of a medicament composition for separating carbon-coated lithium iron phosphate from graphite according to claim 1, characterized in that: The particle size of the object to be separated is less than 100 microns, and the amount of particles with a particle size of less than 100 microns accounts for 85% to 90% of the total particle mass.

6. The use of a medicament composition for separating carbon-coated lithium iron phosphate from graphite according to claim 1, characterized in that: In step B, the pH of the slurry is controlled to be 8 to 9.5 during flotation.

7. The application of the reagent group for separating carbon-coated lithium iron phosphate and graphite by flotation according to claim 1, characterized in that: The amount of the inhibitor is controlled to be 100 g / t to 300 g / t; The ratio of the carboxymethyl cellulose to the sodium sulfite is 1:8 to 1:10.

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