Micro-fine particle flotation method for electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation and control

Abstract

The invention discloses a micro-fine particle flotation method for electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation and control. The method comprises the following steps that the electrolytic aluminum anode carbon slag after lithium extraction is pretreated to obtain carbon slag lithium extraction slag; carrying out ball milling activation on the carbon residue lithium extraction residue; the activated ore pulp is subjected to flotation pretreatment and flotation separation; the carbon concentrate obtained through flotation is subjected to alkaline leaching impurity removal, high-grade carbon concentrate is obtained, and meanwhile tailings can be directly used as regenerated electrolyte. According to the method, the surface performance of the carbon particles is enhanced through ball milling activation, the flotation recovery efficiency and selectivity are improved, synergistic efficient recovery of the carbon and the electrolyte is achieved, and the method has the advantages of being simple and convenient in process, high in recovery rate, environmentally friendly and the like. The grade of the obtained carbon concentrate can reach 85.65%, and the fluorine grade in the tailings is ensured, so that the carbon concentrate can be directly recycled as electrolyte or further recycled.

Description

Technical Field

[0001] The invention relates to the field of comprehensive resource utilization and mineral processing technology, and specifically to a flotation method for fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation. Background Art

[0002] my country's aluminum industry produces over one million tons of electrolytic cell overhaul slag annually. Due to its complex composition and diverse phases, the lack of efficient and economical comprehensive disposal technologies has led to high treatment costs, posing severe economic and environmental pressures to enterprises. This overhaul slag is rich in various toxic and hazardous substances, including cyanide. If stored in an unregulated manner, toxic components can migrate into the surrounding environment through aerosol transmission or leaching, leading to secondary environmental problems such as air pollution, accumulation of heavy metals in soil, and groundwater contamination, while also causing a significant waste of strategic resources such as carbon-based materials and electrolytes. Notably, overhaul slag contains valuable elements such as lithium, fluorine, and carbon. The lithium content can reach 0.5%-2.5% (measured as Li₂O), significantly higher than some low-grade lithium ores. Currently, direct lithium extraction from electrolytic cell overhaul slag is being conducted industrially. However, the leached slag still contains valuable elements such as fluorine and carbon, necessitating the development of efficient separation methods to fully utilize the overhaul slag as a resource.

[0003] Flotation, a mineral processing method that exploits differences in surface hydrophobicity for effective separation, offers advantages such as a short process, low cost, and simple technology. Aluminum electrolytic cell overhaul slag, composed of hydrophobic carbonaceous materials and hydrophilic electrolyte residues, provides an excellent separation foundation for flotation. By adjusting the reagent system, flotation can selectively concentrate carbon-based components in the foam layer, achieving efficient separation. Compared to roasting and vacuum metallurgy methods, carbon slag flotation does not require high-temperature treatment, does not generate fluorine-containing fumes, and the water used in flotation can be recycled, making it the most commonly used method for the comprehensive recycling of anode carbon slag. Therefore, establishing a clean and efficient separation and targeted conversion technology system to extract and utilize high-value-added resources such as high-purity graphite, high-quality carbon, and recycled cryolite from anode carbon slag will not only effectively achieve the coordinated treatment of hazardous waste, but also significantly improve resource recycling efficiency and promote the green and low-carbon development of the aluminum industry.

[0004] Existing technologies for the flotation separation of carbonaceous components from electrolytic aluminum overhaul slag primarily focus on enhancing dissociation and optimizing reagent systems. Patent CN106077036A discloses a method for physically modifying spent cathode material through ultrasonic pretreatment. This method utilizes the ultrasonic cavitation effect to remove electrolytes and contaminants adhering to the surface of graphite particles, improving the graphite's surface hydrophobicity. This method not only reduces the amount of subsequent flotation reagents used, but also increases graphite recovery to 85%-92%. Patent CN115197867A discloses a method for selectively regulating carbon slag using microbial metabolites or enzyme preparations. This method selectively dissolves or passivates electrolytes in the carbon slag through biochemical reactions while maintaining the hydrophobicity of the carbon particle surface. The carbon slag is then treated with a bioregulator prior to flotation separation. This regulator can increase carbon recovery by 10%-15% and reduce electrolyte entrainment to below 5%. Patent CN115228619B proposes a composite flotation enhancer consisting of a non-polar hydrocarbon oil (such as kerosene and diesel) and a polar surfactant (such as sodium lauryl sulfate and fatty acid salts) in a mass ratio of 3:1 to 5:1, forming a "synergistic adsorption layer." This adsorption layer has the ability to selectively adsorb fine carbon particles and electrolytes, significantly improving the recognition and separation efficiency of target particles during the flotation process.

[0005] It is worth noting that the above technology is mainly aimed at the carbon-electrolyte separation of raw overhaul slag, while the overhaul slag treated by the lithium extraction process shows significant changes in properties: the particle size is generally refined to below 10μm, the surface energy increases, resulting in intensified particle agglomeration, and the original hydrophobic properties are changed by the influence of lithium extraction agents. Such fine particles are easily entrained during the flotation process, significantly reducing the grade of carbon-containing products and fluorine-containing products. Existing control methods are difficult to adapt to the complex surface chemical environment after lithium extraction. Therefore, there is an urgent need for a method for recovering carbon and electrolytes from overhaul slag treated by the lithium extraction process. Summary of the Invention

[0006] The purpose of the present invention is to provide a flotation method for fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation. The dissociation degree of the carbon particle surface is enhanced by ball milling activation and the hydrophobicity of the carbonaceous particle surface is enhanced by optimizing the flotation agent system, thereby improving the flotation separation effect. At the same time, the electrolyte components in the tailings are optimized, the carbon recovery rate and fluorine grade are significantly improved, and the resource-based comprehensive utilization of electrolytic aluminum anode carbon slag is realized.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] The present invention provides a flotation method for fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation, comprising the following steps:

[0009] S1. The electrolytic aluminum anode carbon slag after lithium extraction is dried to obtain carbon slag for lithium extraction;

[0010] S2. The carbon slag was activated by ball milling to obtain an activated sample;

[0011] S3. The activated sample is transferred to a flotation tank, the pulp concentration is adjusted and the pulp is prepared to obtain a pulp;

[0012] S4. The slurry is subjected to multi-stage flotation separation using a closed-circuit flotation process of "two coarsening, two scavenging, and one concentrating" to obtain carbon concentrate;

[0013] S5. The carbon concentrate is slurried again, and an alkaline leaching agent is added to perform alkaline leaching treatment to obtain a fluorine-containing leachate and carbon concentrate.

[0014] Furthermore, in step S1, the particle size of the carbon slag lithium extraction slag is 1-20 μm, the carbon content is 12-20%, the fluorine content is 44-47%, the aluminum content is 10%-14%, the sodium content is 24-26%, and the main components include carbon, cryolite and sodium fluoride.

[0015] Furthermore, in step S2, the specific conditions of the ball milling activation process are that the grinding concentration is controlled at 30% to 60%, and the ball milling time is 0.5 to 1 min.

[0016] Ball milling separates carbon and impurities through the scrubbing action between material particles and between the steel balls, helps to separate fresh surfaces and enhance the hydrophobicity of carbon. It reconstructs the surface structure of carbon particles and enhances their activity in a short period of time.

[0017] Furthermore, in step S3, the final concentration of the slurry is 20% to 30%, and the stirring speed of the slurry adjustment is 2000 to 3000 rpm.

[0018] By strengthening the stirring and slurry adjustment, the apparent viscosity of the slurry can be effectively reduced, the dispersion of mineral particles can be promoted and the entrainment can be reduced, thus achieving the best balance between the rheological properties of the slurry and the particle-bubble collision efficiency.

[0019] Furthermore, in step S4, the "two roughing, two scavenging, one finishing" flotation closed-circuit process is specifically as follows: roughing I is performed on the slurry to obtain rougher concentrate 1 and rougher tailings 1; rougher tailings 1 is subjected to roughing II to obtain rougher concentrate 2 and rougher tailings 2; rougher concentrate 1 and rougher concentrate 2 are subjected to finishing, and the resulting concentrate is used as carbon concentrate, and the finished tailings are returned to roughing I; rougher tailings 2 is subjected to scavenging I to obtain scavenging concentrate 1 and scavenging tailings 1; scavenging concentrate 1 is returned to roughing II, and scavenging tailings 1 is subjected to scavenging II to obtain scavenging concentrate 2 and scavenging tailings 2; scavenging tailings 2 is used as the final tailings, and scavenging concentrate 2 is returned to scavenging 1.

[0020] The specific steps of the roughing I, roughing II and cleaning are: adding an inhibitor, a collector and a frother in sequence to carry out flotation; the specific steps of the scavenging I and scavenging II are: adding a collector and a frother in sequence to carry out flotation;

[0021] The collector is composed of kerosene, diesel, dodecane and vegetable oil, with a mass ratio of 0.3-0.7:0.1-0.5:0-0.2:0-0.2, the roughing amount is 100-500 g / t, the scavenging amount is halved compared with the previous operation, and the fine cleaning amount is 100-200 g / t;

[0022] The inhibitor is sodium hexametaphosphate and / or water glass, and the dosage is 50-300 g / t; the foaming agent is No. 2 oil or MIBC, and the dosage is 50-100 g / t. The dosage of the scavenger is halved successively. The dosage of all reagents is relative to the flotation feed.

[0023] Furthermore, the carbon content in the carbon concentrate is 50-70%.

[0024] The tailings obtained by flotation still contain relatively high contents of electrolyte components such as fluorine, aluminum, and sodium. The fluorine content of the tailings is ≥50%, and it has the potential to be recycled as a regenerated electrolyte raw material.

[0025] Furthermore, in step S5, the liquid-to-solid ratio of the slurry adjustment is 5:1 to 10:1.

[0026] Furthermore, in step S5, the alkaline leaching agent is NaOH; the addition of NaOH is calculated based on the contents of fluorine, aluminum, and sodium in the flotation carbon concentrate to convert the contents of cryolite and alumina, and is determined according to the stoichiometric numbers in the following chemical reaction equation for alkaline leaching. The mass ratio of the flotation carbon concentrate to NaOH in the leaching is (1:0.3) to (1:0.6).

[0027] Al2O3+2NaOH+3H2O=2NaAl(OH)4

[0028] Na3AlF6+4NaOH=NaAl(OH)4+6NaF

[0029] Furthermore, in step S5, the process conditions of the alkali leaching treatment are: leaching temperature is 70-90° C., and leaching time is 1-2 hours.

[0030] The carbon concentrate obtained in step S5 has a carbon purity of up to 80-90%. The fluorine-containing leachate is enriched with fluoride, and the fluoride leaching rate is 75-85%, which is subsequently recovered by cooling crystallization, precipitation or membrane separation.

[0031] Beneficial effects of the present invention:

[0032] (1) The method provided by the present invention achieves enhanced surface activity and structural reconstruction of carbon particles in a relatively short ball milling time through the synergistic effect of ball milling activation and interface regulation. Combined with the "two coarsening, two sweeping, and one fine" closed-circuit flotation process, it reduces the entrainment of fine particles while increasing the fluorine content in the flotation tailings, thereby achieving the separation of carbonaceous and electrolyte components.

[0033] (2) The carbon concentrate obtained by the method of the present invention has a carbon purity of up to 80-90%, and a fluoride leaching rate of 75-85%. It can be used as a high-purity carbon raw material in the fields of metallurgical reducing agents, electrode materials or environmentally friendly adsorbents, thereby realizing high-value utilization of resources;

[0034] (3) The method provided by the present invention processes the flotation concentrate through an alkaline leaching process to remove the included electrolytes and improve the purity of the carbon product. It has high resource utilization, simple process and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the process of the present invention;

[0036] Figure 2 This is a flotation separation flow chart in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] Example 1

[0038] The present invention provides a flotation method for fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation. The flow diagram is as follows: Figure 1 As shown, the following steps are included:

[0039] S1. The electrolytic aluminum anode carbon slag after lithium extraction is dried to obtain carbon slag for lithium extraction. The carbon slag for lithium extraction contains 16.13% carbon, 39.8% fluorine, 12.84% aluminum and 21.54% sodium. The main components include carbon, cryolite and sodium fluoride.

[0040] S2. The carbon slag was activated by ball milling with lithium slag, the grinding concentration was 50%, the grinding time was 0.5min, and the activated sample was obtained;

[0041] S3. The activated sample was transferred to a flotation cell, the pulp concentration was adjusted to 20%, and the flotation machine speed was adjusted to 2000 rpm to obtain a pulp;

[0042] S4. The pulp was subjected to multi-stage flotation separation using a closed-circuit flotation process of "two coarsening, two scavenging, and one concentrating" to obtain a carbon concentrate. Water glass was used as a depressant at a dosage of 50 g / t, and a collector was a mixture of kerosene and diesel at a ratio of 1:1 at a dosage of 300 g / t.

[0043] The flotation closed-circuit process of "two roughing, two sweeping and one fine" is as follows Figure 2 As shown, specifically: the slurry undergoes roughing I to obtain rougher concentrate 1 and rougher tailings 1; rougher tailings 1 undergoes roughing II to obtain rougher concentrate 2 and rougher tailings 2; rougher concentrate 1 and rougher concentrate 2 undergo cleaning, and the resulting concentrates serve as carbon concentrates, with the cleaned tailings returned to roughing I; rougher tailings 2 undergoes scavenging I to obtain scavenging concentrate 1 and scavenging tailings 1; scavenging concentrate 1 returns to roughing II, and scavenging tailings 1 undergoes scavenging II to obtain scavenging concentrate 2 and scavenging tailings 2; scavenging tailings 2 serves as the final tailings, and scavenging concentrate 2 returns to scavenging 1.

[0044] The specific steps of the roughing I, roughing II and cleaning are: adding an inhibitor, a collector and a frother in sequence to carry out flotation; the specific steps of the scavenging I and scavenging II are: adding a collector and a frother in sequence to carry out flotation;

[0045] S5. After filtering and drying the carbon concentrate, the fluorine content was determined to be 29.54%. The obtained carbon concentrate was slurried at a liquid-to-solid ratio of 10:1, and then NaOH was added for alkaline leaching. The mass ratio of the material to sodium hydroxide was 1:0.6. The leaching temperature was controlled at 90°C for 2 hours. After leaching, the concentrate was filtered to obtain a fluorine-containing leachate and carbon concentrate.

[0046] After testing, the recovery rate of carbon concentrate obtained by flotation was 86.42%, the carbon grade was 51.01%, the carbon concentrate grade was 83.24%, and the leaching rate of impurity components was 80.24%.

[0047] Comparative Example 1

[0048] Compared with Example 1, the only difference is that in step S2, ball milling activation is not used, and the flotation concentrate is not subjected to leaching and impurity removal treatment, and other conditions remain unchanged.

[0049] The carbon concentrate and tailings obtained in Comparative Example 1 were tested, and it was calculated that the grade of the carbon concentrate obtained by flotation was 48.23%, the recovery rate was 75.36%, and the fluorine grade in the tailings was 45.38%.

[0050] Example 2

[0051] Compared with Example 1, the only difference is that in step S4, the type of flotation reagent is kerosene:diesel in a ratio of 2:1, and other conditions remain unchanged.

[0052] The carbon concentrate and tailings obtained in Example 2 were tested and calculated to have a grade of 50.23% and a recovery of 83.24% for the carbon concentrate obtained by flotation. The fluorine grade in the tailings was 49.58%. The grade of the carbon concentrate obtained after alkali leaching was 80.21%, and the leaching rate of impurity components was 80.01%.

[0053] Example 3

[0054] Compared with Example 1, the only difference is that in step S4, the amount of flotation collector used is 500 g / t, and other conditions remain unchanged.

[0055] The flotation carbon concentrate and tailings obtained in Example 3 were tested and calculated to have a grade of 50.53% for the flotation carbon concentrate, a recovery of 84.63%, and a fluorine grade of 48.52% in the tailings. After alkaline leaching, the carbon concentrate grade was 86.69%, and the leaching rate of impurity components was 81.03%.

[0056] Example 4

[0057] Compared with Example 1, the only difference is that in step S5, the liquid-solid ratio of the carbon concentrate alkali leaching is 5:1, and other conditions remain unchanged.

[0058] The carbon concentrate obtained in Example 1 was subjected to an alkaline leaching experiment, and the leaching rate of impurities was 78.59%. The carbon content in the final carbon concentrate was 82.15%.

[0059] Example 5

[0060] Compared with Example 1, the only difference is that in step S5, the amount of NaOH used in the alkaline leaching of the carbon concentrate is 1:0.3, and other conditions remain unchanged.

[0061] The flotation carbon concentrate obtained in Example 1 was subjected to an alkaline leaching experiment, and the leaching rate of impurities was found to be 78.69%. The carbon content in the final carbon concentrate was 82.47%.

[0062] Example 6

[0063] Compared with Example 1, the only difference is that in step S5, the alkali leaching time of the carbon concentrate is 1 hour, and other conditions remain unchanged.

[0064] The flotation carbon concentrate obtained in Example 1 was subjected to an alkaline leaching experiment, and the leaching rate of impurities was found to be 83.85%. The carbon content in the final carbon concentrate was 85.63%.

[0065] Example 7

[0066] Compared with Example 1, the only difference is that in step S5, the alkali leaching temperature of the flotation carbon concentrate is 70° C., and other conditions remain unchanged.

[0067] The flotation carbon concentrate obtained in Example 1 was subjected to an alkaline leaching experiment, and the leaching rate of impurities was found to be 79.32%. The carbon content in the final carbon concentrate was 81.46%.

[0068] The core innovation of this invention lies in the construction of a synergistic technology system for efficient carbon separation and purification. Through the coupling of process parameters and interface control mechanisms, it achieves efficient dissociation and selective enrichment of the carbon-electrolyte system. In the pretreatment stage, ball milling activation effectively breaks the interfacial bonding between carbon particles and electrolyte components, promoting the dissociation of carbonaceous particles, enhancing the hydrophobicity of the carbon surface, and reducing the risk of mechanical entrainment of impurity components.

[0069] In the flotation separation stage, the present invention constructs an efficient selective separation system by optimizing the synergistic effect of the fluid mechanics environment and the agent adsorption mechanism. A composite ratio of collector combinations is used to form a gradient surface modification layer through the synergistic adsorption effect of different molecular structures, and accurately regulate the wettability difference between carbon and electrolyte minerals. Combining low flotation concentration with enhanced slurry adjustment, while ensuring the dispersion stability of the slurry, the collision probability and adhesion strength of bubbles and particles are enhanced, achieving the selective capture and enrichment of carbon particles. Furthermore, in alkaline leaching, through the coordinated regulation of leaching parameters, impurity components such as fluoride are efficiently dissociated from the carbon surface, while chemical corrosion of the carbon matrix is suppressed, thereby ensuring the structural integrity of the carbonaceous product.

Claims

1. A flotation method for fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation, characterized in that: The following steps are involved: S1. The electrolytic aluminum anode carbon slag after lithium extraction is dried to obtain carbon slag for lithium extraction; S2. The carbon slag was activated by ball milling to obtain an activated sample; S3. The activated sample is transferred to a flotation tank, the pulp concentration is adjusted and the pulp is prepared to obtain a pulp; S4. The slurry is subjected to multi-stage flotation separation using a closed-circuit flotation process of "two coarsening, two scavenging, and one concentrating" to obtain carbon concentrate; S5. The carbon concentrate is slurried again, and an alkaline leaching agent is added to perform alkaline leaching treatment to obtain a fluorine-containing leachate and carbon concentrate.

2. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S1, the carbon slag lithium extraction slag has a particle size of 1 to 20 μm, a carbon content of 12 to 20%, a fluorine content of 44 to 47%, an aluminum content of 10 to 14%, and a sodium content of 24 to 26%. The main components include carbon, cryolite, and sodium fluoride.

3. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S2, the specific conditions of the ball milling activation process are that the grinding concentration is controlled at 30% to 60%, and the ball milling time is 0.5 to 1 minute.

4. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S3, the final concentration of the slurry is 20% to 30%, and the stirring speed of the slurry adjustment is 2000 to 3000 rpm.

5. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S4, the flotation closed-circuit process of "two roughing, two scavenging and one concentrating" is specifically as follows: roughing I is performed on the slurry to obtain rougher concentrate 1 and rougher tailings 1; roughing II is performed on the rougher tailings 1 to obtain rougher concentrate 2 and rougher tailings 2; rougher concentrate 1 and rougher concentrate 2 are concentrating, the obtained concentrates are used as carbon concentrate, and the concentrating tailings are returned to roughing I; rougher tailings 2 are subjected to scavenging I to obtain scavenging concentrate 1 and scavenging tailings 1; scavenging concentrate 1 is returned to roughing II, and scavenging tailings 1 are subjected to scavenging II to obtain scavenging concentrate 2 and scavenging tailings 2; scavenging tailings 2 are used as final tailings, and scavenging concentrate 2 is returned to scavenging 1.

6. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 5, characterized in that: The specific steps of the roughing I, roughing II and cleaning are: adding an inhibitor, a collector and a frother in sequence to carry out flotation; the specific steps of the scavenging I and scavenging II are: adding a collector and a frother in sequence to carry out flotation; The collector is composed of kerosene, diesel, dodecane and vegetable oil, with a mass ratio of 0.3-0.7:0.1-0.5:0-0.2:0-0.2, the roughing amount is 100-500 g / t, the scavenging amount is halved compared with the previous operation, and the fine cleaning amount is 100-200 g / t; The inhibitor is sodium hexametaphosphate and / or water glass, and the dosage is 50-300 g / t; the foaming agent is No. 2 oil or MIBC, and the dosage is 50-100 g / t. The dosage of the scavenger is halved successively. The dosage of all reagents is relative to the flotation feed.

7. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S4, the carbon content in the carbon concentrate is 50-70%.

8. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S5, the liquid-to-solid ratio of the slurry is 5:1 to 10:

1.

9. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S5, the alkaline leaching agent is NaOH; the addition of NaOH is calculated based on the contents of fluorine, aluminum, and sodium in the flotation carbon concentrate, equivalent to the contents of cryolite and alumina, and is determined according to the stoichiometric coefficient of alkaline leaching. The mass ratio of the flotation carbon concentrate to NaOH during leaching is (1:0.3) to (1:0.6).

10. The method for flotation of fine particles of electrolytic aluminum anode carbon slag after lithium extraction based on ball milling activation and interface regulation according to claim 1, characterized in that: In step S5, the process conditions of the alkali leaching treatment are: leaching temperature is 70-90° C., and leaching time is 1-2 hours.

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