A flotation depressant, its preparation method and application

Abstract

The application belongs to the technical field of battery recycling, and discloses a flotation depressant, a preparation method and application thereof. The flotation depressant comprises catechol, an oxidizing agent and a weak acid buffer solution, and the pH value of the flotation depressant is 4-6.5. The catechol and the oxidizing agent are dissolved in the weak acid buffer solution to prepare the flotation depressant, the flotation depressant can selectively inhibit the flotation of the positive electrode material, and thus the positive electrode material and the negative electrode material are separated through reverse flotation. The flotation depressant is used for flotation to obtain the positive electrode material rich in cobalt, and the grade and the recovery rate of the positive electrode material are as high as 90% and 83% respectively. The preparation method of the flotation depressant is simple, the cost is low, the flotation depressant is friendly to the environment, and the flotation depressant has a good application prospect in industrial battery recycling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of battery recycling, and particularly relates to a flotation depressant as well as a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in daily life, military and other fields due to high energy density, safety and convenience of use, and the use amount is increasing day by day. The service life of lithium ion batteries is generally about 2-3 years, and the continuous emergence of new products such as electronic products leads to a large number of lithium ion batteries facing retirement. If the retired lithium ion batteries are not disposed of in time, they will cause great pollution to the environment, and because of the shortage of mineral resources, the metals such as copper, aluminum, lithium and manganese contained in the waste lithium ion batteries are particularly important to be resourceized. There are still some problems in the treatment method of the retired lithium ion batteries. The positive and negative electrode materials of the waste lithium ion batteries are mainly lithium cobalt oxide (LiCoO2) and graphite. Graphite is a non-polar mineral and has very good hydrophobicity; LiCoO2 is an ionic crystal and has good hydrophilicity. Therefore, according to the flotation theory, it is feasible to separate the positive and negative electrode materials by flotation. However, because of the existence of polyvinylidene fluoride (PVDF) on the surface of the positive electrode material, the surface of the positive electrode material is hydrophobic, so the positive and negative electrode materials are not easy to separate, and the recovery rate of the positive and negative electrode materials is low.

[0003] Therefore, it is urgent to provide a flotation reagent which can separate the positive and negative electrode materials well and improve the recovery rate of the positive and negative electrode materials. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a flotation depressant which can selectively inhibit the flotation of the positive electrode material, so as to effectively separate the positive and negative electrode materials by reverse flotation and improve the recovery rate of the positive and negative electrode materials.

[0005] The present application provides a flotation depressant.

[0006] Specifically, a flotation depressant comprises catechol, an oxidizing agent and a weak acid buffer, and the pH value of the flotation depressant is 4-6.5.

[0007] Preferably, the oxidizing agent comprises at least one of soluble persulfate, soluble chlorate and soluble periodate, such as ammonium persulfate, sodium persulfate, potassium persulfate, potassium chlorate, sodium chlorate, sodium periodate and potassium periodate.

[0008] Further preferably, the oxidant is a soluble periodate. Using periodate as an oxidant in the reaction provides a better catalytic effect than persulfate and chlorate; more preferably, the soluble periodate is sodium periodate (SP). Sodium periodate acts as a trigger for oxidative self-polymerization, oxidizing catechol to generate oligomers carrying hydrophilic groups. Some of the hydrophilic carboxyl groups (-COOH) and hydroxyl groups (-OH) carried by the oligomers are deposited on the surface of the positive electrode material particles, increasing the hydrophilicity of the positive electrode material surface. This also gives the positive electrode material bonded with polyvinylidene fluoride (PVDF) good hydrophilicity, enabling separation from the hydrophobic negative electrode material.

[0009] Preferably, the concentration of sodium periodate (SP) is 1-8 mg / mL; more preferably, the concentration of sodium periodate (SP) is 2-6 mg / mL.

[0010] Preferably, the pH value of the flotation inhibitor is 4.5 to 6.5; more preferably, the pH value of the flotation inhibitor is 4.5 to 6.0; and even more preferably, the pH value of the flotation inhibitor is 4.5 to 5.5.

[0011] Preferably, the weakly acidic buffer solution is an acetate buffer solution. Acetate buffer solution controls the pH and, compared to a weakly alkaline buffer solution, can significantly improve the reaction efficiency of flotation inhibitors; moreover, acetate buffer solution is inexpensive, readily available, and relatively safe.

[0012] Preferably, the concentration of catechol is 0.5–10 mg / mL; more preferably, the concentration of catechol is 1–5 mg / mL.

[0013] The present invention also provides a method for preparing flotation inhibitors.

[0014] Specifically, a method for preparing a flotation inhibitor includes the following steps:

[0015] A flotation inhibitor was prepared by mixing catechol, an oxidant, and a weakly acidic buffer solution and reacting them under light-protected conditions until the solution turned brown. The mixture was then allowed to stand.

[0016] Preferably, the reaction process involves placing the mixture in a shaker and reacting it at room temperature (5–40°C). The shaking speed is 80–200 r / min.

[0017] Preferably, the settling time is 1 to 4 hours; more preferably, the settling time is 1.5 to 3 hours, such as 2 hours.

[0018] More specifically, a method for preparing a flotation inhibitor includes the following steps:

[0019] Catechol and an oxidizing agent are dissolved in a weakly acidic buffer solution to obtain a mixture. The mixture is then placed in a shaker and reacted at room temperature (5-40°C) in the dark until the solution turns brown. After standing for 1-4 days, a flotation inhibitor is obtained.

[0020] The present invention also provides the application of the above-mentioned flotation inhibitor.

[0021] Specifically, the above-mentioned flotation inhibitors are used in the separation of positive and negative electrode materials from waste batteries.

[0022] Preferably, the battery is a lithium-ion battery.

[0023] The present invention also provides a method for separating the positive and negative electrode materials of waste batteries.

[0024] Specifically, a method for separating positive and negative electrode materials from waste batteries, using the aforementioned flotation inhibitor, includes the following steps:

[0025] The positive and negative electrode materials of the waste battery are crushed, water is added, and the mixture is stirred to disperse the materials. Then, the above-mentioned flotation inhibitor is added and reacted for 1 to 8 minutes. Collectors and frothers are added in sequence to react. Finally, the positive and negative electrode materials are separated by reverse flotation.

[0026] Preferably, the amount of flotation inhibitor used is 0.02–0.12 mg / L; more preferably, the amount of flotation inhibitor used is 0.04–0.12 mg / L; even more preferably, the amount of flotation inhibitor used is 0.05–0.10 mg / L. Examples include 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, and 0.10 mg / L.

[0027] Preferably, the stirring speed is 1600-1800 r / min.

[0028] Preferably, the collector is dodecane; the amount of the collector is 10-200 mg / L.

[0029] Preferably, the foaming agent is methyl isobutyl alcohol (MIBC).

[0030] Preferably, the reaction time is 2 to 5 minutes; more preferably, the reaction time is 2 to 4 minutes.

[0031] More specifically, a method for separating positive and negative electrode materials from waste batteries, using the aforementioned flotation inhibitor, includes the following steps:

[0032] After the positive and negative electrode materials of the waste batteries are crushed, they are quantitatively added to the flotation cell, water is added, the impeller is turned on, and the material is dispersed by stirring at a speed of 1600-1800 r / min. Then the above-mentioned flotation inhibitor is added and reacted for 1-8 minutes. Then the collector and frother are added in sequence and reacted for 3-10 minutes. After the flotation inhibitor, the collector and the frother have fully reacted, the stirring is continued to carry out the reverse flotation operation to separate the positive and negative electrode materials.

[0033] Catechol (CA) exhibits excellent adhesion to both polar and nonpolar substrates. Under the catalysis of oxidants (especially periodate), the self-polymerization of CA is significantly accelerated, and it can rapidly deposit hydrophilic groups onto polyvinylidene fluoride (PVDF). This results in positive electrode materials bonded with PVDF also possessing good hydrophilicity, enabling effective separation from hydrophobic negative electrode materials. This invention utilizes a flotation inhibitor composed of catechol and periodate to pretreat the surface of the positive electrode material, and then recovers LiCoO2 and graphite from the positive and negative electrode materials through flotation, effectively improving the recovery rate of both materials.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) In this invention, catechol and an oxidant are dissolved in a weakly acidic buffer solution to prepare a flotation inhibitor. This flotation inhibitor selectively inhibits the flotation of the positive electrode material, thereby separating the positive and negative electrode materials through reverse flotation. Using this flotation inhibitor, cobalt-rich concentrate (positive electrode material) can be obtained, with a concentrate (positive electrode material) grade and recovery rate as high as 90% and 83%, respectively.

[0036] (2) The flotation inhibitor provided by this invention can significantly improve the flotation recovery rate and enhance the flotation effect, thereby effectively separating the positive and negative electrode materials and finally obtaining the positive electrode material, which is then sent for further separation. This flotation pretreatment method can effectively avoid the huge energy consumption generated during the pretreatment of waste lithium-ion batteries, and the method is simple and harmless, with potential for industrialization.

[0037] (3) The flotation inhibitor provided by the present invention has a simple preparation method, low cost, and is environmentally friendly, and has a good application prospect in industrial battery recycling. Attached Figure Description

[0038] Figure 1 The figure shows the results of single-mineral flotation recovery of carboxymethyl cellulose for positive and negative electrode materials in Experiment 1.

[0039] Figure 2 The figure shows the results of single-mineral flotation recovery of positive and negative electrode materials by gum arabic in Experiment 1.

[0040] Figure 3This is a graph showing the results of single-mineral flotation recovery of starch for positive and negative electrode materials in Experiment 1;

[0041] Figure 4 The figure shows the results of single-mineral flotation recovery of positive and negative electrode materials by flotation inhibitors in Experiment 1.

[0042] Figure 5 The figure shows the effect of reverse flotation time on the single mineral flotation recovery of positive and negative electrode materials in Experiment 2.

[0043] Figure 6 The figure shows the results of flotation recovery of mixed minerals with positive and negative electrode materials by flotation inhibitors in Experiment 3. Detailed Implementation

[0044] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0045] In Experiments 1 and 2, lithium cobalt oxide, a simulated positive electrode material, was used to replace the positive electrode material of discarded lithium-ion batteries, and graphite was used to replace the negative electrode material. In Experiment 3, the negative electrode material of the discarded lithium battery came from retired Samsung mobile phone lithium batteries, and the positive electrode material was the simulated positive electrode material, lithium cobalt oxide. The preparation process of the simulated positive electrode material, lithium cobalt oxide, is as follows: PVDF is dissolved in N-methylpyrrolidone (NMP), stirred until a gel is formed, and then LiCoO2 is added to bind the LiCoO2 and PVDF together. Finally, NMP is removed to obtain lithium cobalt oxide with 5% PVDF bonded to its surface.

[0046] Unless otherwise specified, all other raw materials, reagents or apparatus are available from conventional commercial sources or can be obtained by existing known methods.

[0047] Example 1

[0048] A flotation inhibitor is composed of catechol (CA), sodium periodate (SP), and acetate buffer, wherein the concentration of catechol is 2 mg / mL, the concentration of sodium periodate is 4 mg / mL, the acetate buffer is 50 mM, and the pH value of the flotation inhibitor is 5.0.

[0049] The preparation method of this flotation inhibitor is as follows:

[0050] Under normal temperature conditions, catechol (CA), sodium periodate (SP), and acetate buffer are mixed in proportion, the container opening is covered with aluminum foil to protect it from light, and the mixed solution is placed in a shaker (120 r / min) at room temperature. The reaction is carried out until the solution turns brownish-brown, and finally it is allowed to stand for 2 hours to obtain the flotation inhibitor.

[0051] Example 2

[0052] A flotation inhibitor is composed of catechol (CA), sodium periodate (SP), and acetate buffer, wherein the concentration of catechol is 3 mg / mL, the concentration of sodium periodate is 6 mg / mL, the acetate buffer is 45 mM, and the pH value of the flotation inhibitor is 5.5.

[0053] The preparation method of this flotation inhibitor is as follows:

[0054] Under normal temperature conditions, catechol (CA), sodium periodate (SP), and acetate buffer are mixed in proportion, the container opening is covered with aluminum foil to protect it from light, and the mixed solution is placed in a shaker (120 r / min) at room temperature. The reaction is carried out until the solution turns brownish-brown, and finally it is allowed to stand for 2 hours to obtain the flotation inhibitor.

[0055] Example 3

[0056] A flotation inhibitor is composed of catechol (CA), sodium periodate (SP), and acetate buffer, wherein the concentration of catechol is 5 mg / mL, the concentration of sodium periodate is 6 mg / mL, the acetate buffer is 50 mM, and the pH value of the flotation inhibitor is 5.0.

[0057] The preparation method of this flotation inhibitor is as follows:

[0058] Under normal temperature conditions, catechol (CA), sodium periodate (SP), and acetate buffer are mixed in proportion, the container opening is covered with aluminum foil to protect it from light, and the mixed solution is placed in a shaker (120 r / min) at room temperature. The reaction is carried out until the solution turns brownish-brown, and finally it is allowed to stand for 2 hours to obtain the flotation inhibitor.

[0059] Experiment 1

[0060] This study investigates the inhibitory effects of different flotation inhibitors on the positive and negative electrode materials of batteries.

[0061] The positive and negative electrode material powders were fed into a flotation cell (50 mL) for single flotation experiments. During the single flotation process, 1 g of each material was added, followed by 50 mL of ultrapure water. The impeller was turned on and stirred at a speed of 1600–1800 r / min for 2 minutes to ensure complete dispersion of the material in the cell, yielding a flotation slurry. The active substances in the positive electrode material were mainly LiCoO2 and PVDF, while the active substances in the negative electrode material were mainly graphite. Different inhibitors (different concentrations of carboxymethyl cellulose, gum arabic, starch, and the flotation inhibitor prepared in Example 1) were added to the positive and negative electrode flotation slurries and reacted for 3 minutes. Then, dodecane (100 mg / L) was added as a collector and reacted for 3 minutes. Finally, MIBC (5 mg / L) was added as a frother and reacted for 1 minute. The impeller continued stirring at a speed of 1600–1800 r / min to ensure the reagents were fully adsorbed onto the material surface and modified, allowing for reverse flotation and foam removal. After flotation, the recovery of single minerals for both positive and negative electrode materials by each inhibitor is as follows: Figures 1 to 4 As shown. After Figures 1 to 4 It was found that compared with the flotation inhibitor provided by this invention, the polysaccharide inhibitor had a less significant effect on the positive electrode material, failing to separate the positive and negative electrode materials, resulting in poor flotation performance. Further comparison of the flotation performance with and without the flotation inhibitor provided by this invention yielded the following results: Figure 4 As shown, through Figure 4 It was found that without flotation inhibitors, the single flotation recovery rate of the positive electrode material was 65%. After adding the inhibitors, the positive electrode material was significantly suppressed, and the suppression effect was strong, causing the recovery rate to drop rapidly to close to 0%. At this time, the recovery rate of the negative electrode material was greater than 90% (the concentration of the flotation inhibitor was 0.03 mg / L), which enabled the effective separation of the positive and negative electrode materials. Thus, subsequent separation can improve the final recovery rate of the positive and negative electrode materials.

[0062] Experiment 2

[0063] This study investigates the effect of the reaction time of flotation inhibitors on the inhibitory effect on the positive and negative electrode materials of batteries.

[0064] The positive and negative electrode material powders were fed into a flotation cell (50 mL) for single flotation experiments. During the single flotation process, 1 g of each material was added, followed by 50 mL of ultrapure water. The impeller was turned on and stirred at a speed of 1600–1800 r / min for 2 minutes to ensure complete dispersion of the material in the cell, yielding a flotation slurry. The active substances in the positive electrode material were mainly LiCoO2 and PVDF, while the active substances in the negative electrode material were mainly graphite. The flotation inhibitor (0.02 mg / L) prepared in Example 1 was added to the positive and negative electrode material flotation slurries and reacted for 0, 2, 4, 6, and 8 minutes respectively. Then, the collector dodecane (100 mg / L) was added and reacted for 3 minutes. Finally, the frother MIBC (5 mg / L) was added and reacted for 1 minute. The impeller continued stirring at a speed of 1600–1800 r / min to ensure the reagents were fully adsorbed onto the material surface and modified, allowing for reverse flotation and foam removal. After flotation, the effects of flotation inhibitors on the single-mineral flotation recovery of positive and negative electrode materials at different reaction times are as follows: Figure 5 As shown. By Figure 5 It can be seen that as time increases, the recovery rate of the positive electrode material will reach an optimal recovery point, that is, when the reaction time is 3 minutes, the difference in flotation recovery rate between the positive and negative electrode materials is the largest, and the positive and negative electrode materials can be effectively separated to the greatest extent.

[0065] It should be noted that in Experiments 1 and 2, single-mineral flotation was performed, and the yield was the recovery rate.

[0066] Experiment 3

[0067] This study investigates the effects of different concentrations of flotation inhibitors on the inhibition of positive and negative electrode materials in batteries.

[0068] The positive and negative electrode material powders of waste lithium batteries were fed into a flotation cell (50mL) for mixed flotation experiments. During the mixed flotation process, 1g of each positive and negative electrode material was added, and 50mL of ultrapure water was added to the flotation cell. The impeller was turned on and the speed was controlled at 1600-1800r / min. The stirring was continued for 2min to ensure that the material was completely dispersed in the cell, and the flotation slurry was obtained. The active materials of the positive electrode material in the flotation slurry were mainly LiCoO2 and PVDF, and the active materials of the negative electrode material were mainly graphite. Different concentrations of flotation inhibitors prepared in Example 1 (0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06 mg / L) were added to the flotation pulp and reacted for 3 min. Then, dodecane (100 mg / L) was added as a collector and reacted for 3 min. Finally, MIBC (5 mg / L) as a frother was added and reacted for 1 min. The impeller continued stirring at a speed controlled at 1600–1800 r / min to ensure that the reagents were fully adsorbed onto the material surface and modified, thus performing reverse flotation and foam removal. After flotation, the recovery of mixed minerals for battery positive and negative electrode materials by different concentrations of flotation inhibitors was as follows:Figure 6 As shown. In Figure 6 In the graph, the horizontal axis represents the concentration of flotation inhibitor (CA-SP), and the vertical axis represents the cathode material recovery rate and cathode material grade, respectively. Cathode material recovery rate (mixed flotation) = weight of cathode material after high-temperature (A℃) PVDF removal from tailings after flotation ÷ (total weight of cathode material before flotation - weight of PVDF (5%)); Grade (mixed flotation) = (weight of cathode material after high-temperature PVDF removal from tailings after flotation * 1.05) ÷ weight of cathode material in tailings after flotation. Because mixed flotation uses simulated cathode material, and 5% PVDF is added during cathode material production, a coefficient of 1.05 is used.

[0069] Depend on Figure 6 It can be seen that without flotation depressants, the recovery rate of the positive electrode material is 43%, and the grade is 84.92%. At this point, a large amount of positive electrode material will float to the surface with the bubbles, making it impossible to effectively separate the positive and negative electrode materials. When a flotation depressant with a concentration of 60 mg / L is added, the recovery rate of the positive electrode material is 90%, and the grade is 83%. At this point, the selective inhibition effect of the reagent is strong, which can effectively avoid the huge energy consumption generated during the pretreatment of waste lithium-ion batteries. Moreover, this method is simple and harmless, and has the potential for industrialization.

[0070] Tests showed that the flotation inhibitors prepared in Examples 2 and 3 achieved similar effects to those in Example 1, both exhibiting good inhibition of the positive electrode material and enabling effective separation of the positive and negative electrode materials.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A flotation inhibitor, characterized in that, It includes catechol, an oxidant, and a weakly acidic buffer solution, wherein the pH value of the flotation inhibitor is 4 to 6.5; The oxidant includes at least one of soluble persulfate, soluble chlorate, and soluble periodate; The weakly acidic buffer solution is an acetate buffer solution.

2. The flotation depressant according to claim 1, characterized in that, The soluble periodate is sodium periodate.

3. The flotation depressant according to claim 2, characterized in that, The concentration of sodium periodate is 1–8 mg / mL.

4. The flotation depressant according to claim 1, characterized in that, The pH value of the flotation inhibitor is 4.5~6.

5.

5. The flotation depressant according to any one of claims 1 to 4, characterized in that, The concentration of the catechol is 0.5–10 mg / mL.

6. The method for preparing the flotation inhibitor according to any one of claims 1 to 5, characterized in that, Includes the following steps: A flotation inhibitor was prepared by mixing catechol, an oxidant, and a weakly acidic buffer solution and reacting them under light-protected conditions until the solution turned brown. The mixture was then allowed to stand.

7. The application of the flotation inhibitor according to any one of claims 1 to 5 in the separation of positive and negative electrode materials of waste lithium-ion batteries.

8. A method for separating positive and negative electrode materials from waste batteries, characterized in that, Separation using any one of the flotation depressants according to claims 1 to 5 includes the following steps: The positive and negative electrode materials of the waste batteries are crushed, water is added, and the mixture is stirred to disperse the materials. Then, a flotation inhibitor is added and reacted for 1 to 8 minutes. Collectors and frothers are added in sequence and reacted. Finally, the positive and negative electrode materials are separated by reverse flotation.

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