CN117701911A - A method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste - Google Patents

Abstract

The invention discloses a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid wastes. According to the invention, aiming at one or more dangerous solid wastes produced in the aluminum electrolysis process, a calcium source roasting-water leaching-purifying process is adopted, the aluminum electrolysis dangerous solid wastes and a calcium source are mixed and roasted, so that a water-insoluble lithium-containing phase is converted into a water-soluble lithium salt after roasting, phases of aluminum, fluorine and the like are converted into water-insoluble phases, and then the preferential extraction and separation of lithium in the aluminum electrolysis dangerous solid wastes can be realized through simple water leaching. Aiming at lithium-containing aluminum electrolysis dangerous solid waste, the invention can realize the preferential extraction of lithium, and simultaneously, fluorine and aluminum in a lithium-containing object phase are precipitated into slag, so that the concentration of aluminum and fluorine in the obtained lithium-rich solution is lower, the problems of large lithium slag loss, low recovery rate and the like caused by the adsorption of lithium by neutralizing precipitated slag in the traditional process are avoided, and the harmless and recycling of the aluminum electrolysis dangerous solid waste are realized.

Description

A method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste

Technical field

The present invention relates to the technical field of resource recovery of industrial solid waste, and specifically relates to a method for preferentially extracting lithium from aluminum electrolysis hazardous solid waste containing lithium, especially preferentially extracting aluminum electrolysis hazardous solid waste such as carbon residue generated during the aluminum smelting process. , overhaul slag, cathode dust, aluminum dust, waste electrolyte, etc., and achieve efficient separation of lithium from fluorine and aluminum.

Background technique

Lithium-containing aluminum electrolysis hazardous solid waste mainly includes carbon slag, overhaul slag, cathode ash, aluminum ash and waste electrolyte. These aluminum electrolysis hazardous solid waste are all lithium-containing resources. As an additive to aluminum electrolyte, lithium salt plays a very important role in the electrolytic aluminum industry. It can significantly reduce the primary crystallization temperature of aluminum electrolyte, increase conductivity, and save energy and consumption. According to theoretical and practical proof, the aluminum electrolyte system containing 1.5% to 2.5% lithium salt (such as lithium fluoride) can maintain the optimal state of the electrolysis process. Since low-grade bauxite contains lithium, as the alumina raw materials continue to be enriched in the electrolytic tank, the lithium content in the electrolyte will also continue to be enriched. The lithium salt content in some aluminum plants can even reach 6% to 10%. This high-lithium electrolyte will have a certain negative effect on the aluminum electrolysis process and even affect the normal operation of the electrolytic cell. In the aluminum electrolysis production process, due to electrolytic cell maintenance and production adjustment, waste electrolytes and hazardous solid wastes that entrain or entrain electrolytes, such as carbon slag, cathode ash, overhaul slag, etc., will be produced. Therefore, this part of aluminum electrolysis solid waste materials will have Higher lithium content. Currently, lithium resources are in short supply, with demand exceeding supply and prices remaining high. Therefore, extracting lithium elements from hazardous solid waste of aluminum electrolysis through reasonable processes and expanding the recycling of lithium resources are of great importance to both the aluminum electrolysis industry and lithium salt production. economic value and practical significance.

However, the existing methods for extracting lithium from aluminum electrolysis hazardous solid waste are to leach lithium, fluorine and aluminum at the same time, and then gradually separate them through neutralization and precipitation. (AlF _x (OH) _3-x ·nH ₂ O) has hydrophilic hydroxyl groups and is easy to adsorb lithium ions. Therefore, the recovery process has shortcomings such as long process flow, complex leachate composition, and low comprehensive lithium recovery rate.

Therefore, the existing technology still needs to be improved and developed.

Contents of the invention

In view of the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste, aiming to solve the existing process of extracting lithium from aluminum electrolysis hazardous solid waste. The process is long, the leachate composition is complex, and the comprehensive recovery rate of lithium is low.

A first aspect of the present invention provides a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste, which includes the steps:

(1) The lithium-containing aluminum electrolysis hazardous solid waste is crushed and refined, and then mixed with a calcium source to obtain a mixture;

(2) Perform roasting treatment on the mixture to obtain roasted material;

(3) The roasted material is crushed and refined and then immersed in water to obtain a slurry. The slurry is separated from liquid and solid to obtain a water immersion liquid;

(4) Evaporate and concentrate the water immersion liquid to obtain a lithium-rich concentrated liquid;

(5) Add alkali to adjust the pH value of the lithium-rich concentrated solution to neutralize and remove impurities, and then filter to obtain a lithium-rich purified solution;

(6) Add a lithium precipitation agent and an alkali to the lithium-rich purification solution to neutralize the lithium precipitation, and then filter it to obtain a lithium salt.

The above method also includes steps:

In step (3), while the water leaching liquid is obtained through liquid-solid separation of the slurry, water leaching residue is also obtained;

The water-leached residue is washed multiple times until the washing liquid becomes neutral, and the water-washing liquid and water-washing residue are obtained by filtration. The water-leaching liquid is returned to the water-leaching process of step (3) for reuse.

In step (5), while the lithium-rich purification liquid is obtained through filtration, fluoroaluminum slag is also obtained.

The water-washed slag and fluoroaluminum slag are mixed to comprehensively recover valuable elements such as fluorine, aluminum, and calcium.

In step (6), while filtering to obtain the lithium salt, a lithium precipitation filtrate is also obtained, and the lithium precipitation filtrate is returned to the water immersion process of step (3) for reuse.

That is to say, the present invention is a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste, as shown in Figure 1, which specifically includes the steps:

1) Crush and refine the lithium-containing aluminum electrolysis hazardous solid waste (such as carbon slag, overhaul slag, cathode ash, waste electrolyte), and then mix it with a calcium source to obtain a mixture;

2) Perform roasting treatment on the mixture to obtain roasted material;

3) The roasted material is crushed and refined and then leached in water to obtain a slurry. The slurry is separated from liquid and solid to obtain water leaching residue and water leaching liquid;

4) Wash the water-leached residue multiple times until the washing liquid becomes neutral, filter to obtain the water-washing liquid and the water-washing residue, and return the water-leaching liquid to the water-leaching process of step 3) for reuse;

5) Evaporate and concentrate the water immersion liquid to obtain a lithium-rich concentrated liquid;

6) Add alkali to adjust the pH value of the lithium-rich concentrated solution, neutralize and remove impurities (time is more than 0.5h), and filter to obtain lithium-rich purification solution and fluoroaluminum slag;

7) Add lithium precipitation agent and alkali to the lithium-rich purification solution to neutralize the lithium precipitation, and then filter (i.e. solid-liquid separation) to obtain lithium salt and lithium precipitation filtrate, and the lithium precipitation filtrate is returned to step 3) Water soaking process is reused;

8) Mix the water-washed slag obtained in step 4) and the fluoroaluminum slag obtained in step 6) to comprehensively recover fluorine, aluminum, calcium and other valuable elements.

The present invention provides a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste. For one or more hazardous solid wastes produced during the aluminum electrolysis process, a calcium source roasting-water leaching-purification process is adopted. Specifically, Thoroughly mix the aluminum electrolysis hazardous solid waste with the calcium source and roast it, so that the water-insoluble lithium-containing phase (such as LiNa ₂ AlF ₆ , LiF, etc.) is converted into water-soluble lithium salt after roasting, and the aluminum The fluorine in the electrolysis of hazardous solid waste is converted into water-insoluble calcium fluoride (CaF ₂ ), and the aluminum is converted into water-insoluble aluminum oxide (Al ₂ O ₃ ). Then the aluminum electrolysis of hazardous solids can be achieved through simple water immersion. Preferential extraction and separation of lithium from waste residues. This invention is aimed at hazardous solid waste from aluminum electrolysis containing lithium, and can realize the preferential extraction of lithium. At the same time, the fluorine and aluminum in the lithium-containing phase are precipitated into the slag, so that the concentrations of aluminum and fluorine in the obtained lithium-rich solution are both low, which avoids It solves the problems of large lithium slag loss and low recovery rate caused by the adsorption of lithium by the neutralization precipitation slag under the traditional process. The phases of fluorine and aluminum elements in the lithium slag are mainly CaF ₂ and Al ₂ O ₃ , which can realize the risk of aluminum electrolysis. The harmless and high-value utilization of solid waste residues can be used for subsequent resource recycling. Compared with the existing technology, the present invention has obvious advantages such as simple process, easy control of process, low cost, and high lithium recovery rate.

The reaction equation involved in the present invention is as follows:

Among them, 1≤x≤3, 3≤y≤5.

In step 1), the lithium-containing aluminum electrolytic hazardous solid waste is crushed and refined, and then fully mixed with the calcium source in a certain proportion to obtain a mixture.

Further, the lithium-containing aluminum electrolysis hazardous solid waste is selected from one or more of overhaul slag, carbon slag, cathode ash, aluminum ash, and waste electrolyte.

Further, after the lithium-containing aluminum electrolysis hazardous solid waste is crushed and refined, the average particle size reaches below -50 mesh.

Further, the calcium source is selected from calcium-containing materials, and the calcium-containing materials are selected from one or more of calcium oxide, calcium carbonate, calcium sulfate, calcium nitrate, calcium hydroxide, calcium peroxide, and calcium hypochlorite. species; preferably one or more of calcium sulfate, calcium hydroxide, and calcium carbonate. The Ca element and fluorine element in the calcium-containing material can form calcium fluoride that is poorly soluble in water.

Further, according to the stoichiometric ratio required for the added calcium element and the fluorine element in the aluminum electrolysis hazardous solid waste to form calcium fluoride, the excess coefficient of the aluminum electrolysis hazardous solid waste and the calcium source can be selected from 1 to 2 .

Further, the crushed and refined aluminum electrolytic hazardous solid waste and the calcium source are thoroughly mixed evenly through a ball mill, grinder or mixer.

In step 2), the mixture obtained in step 1) is roasted to obtain roasted material.

Further, the parameters of the roasting treatment include: the roasting temperature is 300-1000°C, such as 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, etc.; preferably 600-800°C ℃;

The roasting time is 0.5 to 8h, such as 0.5h, 2h, 4h, 6h, 8h, etc.; preferably 1 to 6h;

The roasting atmosphere is any one of air, compressed air, oxygen, and oxygen-rich gas;

The calcination gas pressure is any value within the range of 1 to 2 standard atmospheres, preferably any value within the range of 1 to 1.5 standard atmospheres.

In step 3), the roasted material obtained in step 2) is crushed and refined and then leached in water to obtain a slurry. The slurry is separated from liquid and solid to obtain water leaching residue and water leaching liquid.

Further, the particle size of the roasted material after crushing and refinement is any particle size between -50 mesh and -400 mesh, such as -50 mesh, -100 mesh, -200 mesh, -300 mesh, -400 mesh. Head etc.

Further, the leaching liquid used in the water leaching is a water-containing solution, and the water-containing solution is selected from one of a water-containing neutral solution, a weakly acidic aqueous solution, and a weakly alkaline aqueous solution; the water-containing neutral solution The acidic solution is such as reclaimed water, tap water, deionized water, distilled water, etc.; the weakly acidic aqueous solution is a weakly acidic solution with pH ≥ 5.5; the weakly alkaline aqueous solution is a weakly alkaline solution with pH ≤ 8.

Further, the parameters of the water leaching include: the liquid-to-solid ratio (i.e., the ratio of the volume of the leachate to the weight of the roasted material after crushing and refinement, mL:g) is 2:1 to 10:1, such as 2:1 , 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, preferably 4:1 to 9:1;

The water immersion time is 0.5~6h, such as 0.5h, 1h, 2h, 4h, 5h, 6h, etc.; preferably 1.5~4h;

The water immersion temperature is 50-90°C, such as 50°C, 60°C, 70°C, 80°C, 90°C, etc.; preferably 60-80°C.

In step 4), the water leaching residue obtained in step 3) is washed multiple times until the washing liquid becomes neutral, and filtered to obtain the water washing liquid and water washing slag. The water washing liquid obtained by the above washing is returned to the water leaching process in step 3) for reuse. .

Further, the number of washings is 1 to 6 times, such as 1 time, 2 times, 3 times, 4 times, 5 times, 6 times, etc.; preferably 3 to 5 times;

The liquid-to-solid ratio of each washing (that is, the ratio of the volume of the washing liquid to the weight of the water-leached residue mL:g) is 1:1 to 5:1, such as 1:1, 2:1, 3:1, 4:1 , 5:1, etc.; preferably 2:1 to 3:1;

The washing temperature is 25-70°C, such as 25°C, 35°C, 45°C, 55°C, 60°C, 70°C, etc.; preferably 30-50°C.

Washing time is 0.5-2h.

In step 5), the water leaching liquid is concentrated and enriched to obtain a lithium-rich concentrated liquid.

Further, the concentration multiple of the water immersion liquid for concentration and enrichment is determined according to the lithium ion concentration in the water immersion liquid. The concentration of lithium ions in the lithium-rich concentrated liquid is controlled to be 2-20g/L, such as 2g/L, 6g/L, 8g/L, 10g/L, 14g/L, 16g/L, 20g/L, etc.; preferably 10 to 12g/L.

In step 6), alkali is added to adjust the pH value of the lithium-rich concentrated liquid obtained in step 5) to neutralize and remove impurities. After filtration, a lithium-rich purified liquid and fluoroaluminum slag are obtained.

Further, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, quicklime, and calcium hydroxide, and the pH value of the lithium-rich concentrated liquid is adjusted to any value within the range of 7.5 to 9.5. A value, such as 7.5, 8.0, 8.5, 9.0, 9.5, etc.; preferably any value within the range of 8 to 9.

In step 7), add a lithium precipitation agent and an alkali to the lithium-rich purification liquid obtained in step 6) to neutralize the precipitated lithium, then filter to obtain the lithium salt and the lithium precipitation filtrate, and circulate the lithium precipitation filtrate to the water immersion in step 3). Process reuse.

Further, the lithium precipitation agent used to precipitate lithium from the lithium-rich purification liquid is one of sodium carbonate, carbonic acid, trisodium phosphate, and phosphoric acid.

Further, the base is selected from one or more of sodium hydroxide, ammonia, and sodium metaaluminate, and the pH value of the filtrate is adjusted to any value in the range of 10 to 13, such as 10, 11, 12, 13 wait.

Beneficial effects: The present invention roasts lithium-containing aluminum electrolysis hazardous solid waste (such as carbon slag, overhaul slag, waste cathode, aluminum ash, waste electrolyte, etc.) with calcium sources to convert insoluble lithium salts into water-soluble lithium salts. Physical phase, aluminum, fluorine and other physical phases are further transformed into water-insoluble phases, and then through a simple water leaching reaction, lithium can be extracted preferentially, lithium and fluorine aluminum solid waste can be efficiently separated, and the lithium obtained by water leaching can be Fluorine and aluminum solid waste can meet the requirements for harmless disposal. At the same time, the lithium-rich solution obtained by the present invention contains less fluorine and aluminum impurities, and can avoid the problem of large lithium loss caused by the adsorption of lithium by the slag produced in the subsequent neutralization and precipitation process. Compared with the existing technology, the present invention has obvious advantages such as simple process, easy control of the process, low cost, and high lithium recovery rate.

Description of the drawings

Figure 1 is a schematic flow chart of the method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to the present invention.

Figure 2 is the XRD pattern of the roasted material of Example 1.

Figure 3 is the XRD pattern of the water-leached slag of Example 1.

Figure 4 is an XRD pattern of the lithium precipitation product in Example 1.

Figure 5 is the XRD pattern of the roasted material of Example 2.

Figure 6 is the XRD pattern of the water-leached slag of Example 2.

Figure 7 is an XRD pattern of the lithium precipitation product of Example 5.

Detailed ways

The present invention provides a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste. In order to make the purpose, technical solution and effect of the present invention clearer and clearer, the present invention will be further described in detail below. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

Existing methods for extracting lithium from aluminum electrolysis hazardous solid waste have shortcomings such as long process flow, complex leachate composition, and low comprehensive recovery rate of lithium. Therefore, it is particularly important to find a method to preferentially extract lithium and achieve harmless disposal of hazardous solid waste from aluminum electrolysis. The invention provides a method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste. The lithium-containing aluminum electrolysis hazardous solid waste is roasted using a calcium source, and the lithium-containing material is phase-converted into soluble matter in an air or oxygen atmosphere. The lithium salt simultaneously converts fluorine and aluminum in the hazardous solid waste of aluminum electrolysis into water-insoluble calcium fluoride and aluminum oxide. It only requires simple water immersion to achieve priority extraction of lithium, and the water-washed residue can meet the requirements of harmless According to chemical disposal requirements, the resulting lithium-rich solution contains less fluorine and aluminum impurities, which can avoid the problem of large lithium losses caused by the adsorption of lithium by the slag produced during the neutralization and precipitation process. Compared with the existing technology, the present invention has obvious advantages such as simple process, easy control of the process, low cost, and high lithium recovery rate.

The present invention will be further described below through specific examples.

The main components of hazardous solid waste electrolyzed using lithium-containing aluminum in the embodiments of the present invention are shown in Table 1.

Table 1. Main components of hazardous solid waste from aluminum electrolysis containing lithium

Example 1

(1) Ball mill the lithium-containing carbon residue (containing 40% fluorine and 0.43% lithium) to -100 mesh, and then mix it thoroughly with calcium sulfate at a mass ratio of 100:143 and an excess coefficient of 1 to obtain a mixture.

(2) Put the mixture obtained in step (1) into the roasting furnace. Under an air atmosphere, the gas partial pressure in the furnace is 1 standard atmosphere, and then the temperature is raised to 800°C at a heating rate of 5°C/min and roasted for 2 hours. The roasted material was obtained. After XRD analysis, the physical phase of the roasted material is shown in Figure 2.

(3) Grind the roasted material obtained in step (2) to -100 mesh accounting for 85%, add deionized water, soak it in water at a temperature of 70°C for 2 hours according to a liquid-to-solid ratio of 10mL:1g, and then separate the liquid and solid to obtain water. Leaching residue and water leaching liquid, water leaching residue was analyzed by XRD, and the physical phase is shown in Figure 3.

(4) Evaporate and concentrate the water immersion liquid obtained in step (3) to a concentration factor of 8 times to obtain a lithium-rich concentrated liquid.

(5) Use sodium hydroxide to neutralize the lithium-rich concentrated liquid obtained in step (4), adjust the pH value of the system to 8.5, and filter out impurities after a period of reaction to obtain a lithium-rich purified liquid and fluoroaluminum slag.

(6) Add sodium carbonate to the lithium-rich purification liquid obtained in step (5) (the amount added is 1.3 times the theoretical lithium carbonate production amount), and the precipitated precipitate is filtered to obtain lithium carbonate. The lithium leaching rate in the water leaching process reaches 89.99%. , the recovery rate of lithium in the entire process is 85.23%. The phase of the precipitated lithium product is analyzed by XRD, as shown in Figure 4.

(7) Mix the water-washed slag and fluoroaluminum slag to comprehensively recover the valuable elements of fluorine, aluminum and calcium.

Example 2

(1) Ball mill the lithium-containing carbon residue (containing 40% fluorine and 0.43% lithium) to -200 mesh, and then mix it with mixed calcium (the mass ratio of calcium sulfate and calcium hydroxide is 2:1) at a mass ratio of 100: 120, the excess coefficient is 1, mix thoroughly to obtain a mixture.

(2) Put the mixture into the roasting furnace. In the air atmosphere, the pressure in the furnace is 1 standard atmosphere, and then the temperature is raised to 700°C at a heating rate of 10°C/min. The roasted material is roasted for 4 hours to obtain the roasted material. The roasted material is analyzed by XRD , the physical phase is shown in Figure 5.

(3) Grind the roasted material obtained in step (2) to -200 mesh accounting for 85%, add distilled water, and perform water immersion at a temperature of 60°C for 4 hours according to a liquid-to-solid ratio of 6 mL: 1 g. After liquid-solid separation, the water leaching residue is obtained and water leaching liquid, and the water leaching residue was analyzed by XRD, and the physical phase is shown in Figure 6.

(4) Evaporate and concentrate the water immersion liquid with a concentration factor of 6 times to obtain a lithium-rich concentrated liquid.

(5) Use sodium hydroxide to neutralize the lithium-rich concentrated liquid obtained in step (4), adjust the pH value of the system to 9, filter out impurities after a period of reaction, and obtain lithium-rich purified liquid and fluoroaluminum slag.

(6) Add sodium carbonate to the lithium-rich purification liquid obtained in step (5) (the amount added is 1.3 times the theoretical lithium carbonate production amount), and the precipitated precipitate is filtered to obtain lithium carbonate. The lithium leaching rate in the water leaching process reaches 93.56%. , the lithium recovery rate in the entire process reaches 88.23%.

(7) Mix the water-washed slag and fluoroaluminum slag to comprehensively recover the valuable elements of fluorine, aluminum and calcium.

Example 3

(1) Crush and ball mill the lithium-containing overhaul slag (containing 14% fluorine and 0.54% lithium) to -200 mesh, and then mix it thoroughly with calcium sulfate at a mass ratio of 100:50 and an excess coefficient of 1 to obtain a mixture material.

(2) Put the mixture into the roasting furnace. In the air atmosphere, the pressure in the furnace is 1 standard atmosphere, and then the temperature is raised to 700°C at a heating rate of 5°C/min and roasted for 4 hours to obtain the roasted material.

(3) Grind the roasted material obtained in step (2) to -200 mesh accounting for 85%, add deionized water, soak it in water at a temperature of 80°C for 4 hours according to a liquid-to-solid ratio of 10mL:1g, and obtain water after liquid-solid separation. Leaching residue and water leaching liquid.

(4) Evaporate and concentrate the water immersion liquid with a concentration factor of 8 times to obtain a lithium-rich concentrated liquid.

(5) Use sodium hydroxide to neutralize the lithium-rich concentrated liquid obtained in step (4), adjust the pH value of the system to 9, and filter out impurities after a period of reaction to obtain a lithium-rich purified liquid and fluoroaluminum slag.

(6) Add sodium carbonate to the lithium-rich purification solution (the amount added is 1.3 times the theoretical amount of lithium carbonate produced), precipitate and filter to obtain lithium carbonate. The lithium leaching rate in the water leaching process reaches 83.84%, and the lithium recovery rate in the entire process reaches 75.36%.

(7) Mix the water-washed slag and fluoroaluminum slag to comprehensively recover the valuable elements of fluorine, aluminum and calcium.

Example 4

(1) Grind the waste electrolyte containing lithium (containing 33% fluorine and 1.03% lithium) to -200 mesh, and then mix it with mixed calcium (mass ratio of calcium oxide and calcium hydroxide 4:1) in a mass ratio of 100:62, Mix thoroughly with an excess coefficient of 1.2 to obtain a mixture.

(2) Put the mixture into the roasting furnace. In the air atmosphere, the pressure in the furnace is 1 standard atmosphere, and then the temperature is raised to 600°C at a heating rate of 10°C/min and roasted for 4 hours to obtain the roasted material.

(3) Grind the roasted material obtained in step (2) to -200 mesh accounting for 85%, add distilled water, and perform water immersion at a temperature of 70°C for 1 hour according to a liquid-to-solid ratio of 8 mL: 1 g. After liquid-solid separation, the water leaching residue is obtained and water infusion.

(4) Evaporate and concentrate the water immersion liquid with a concentration factor of 6 times to obtain a lithium-rich concentrated liquid.

(5) Use sodium hydroxide to neutralize the lithium-rich concentrated solution obtained in step (4), adjust the pH value of the solution to 8.5, and filter out impurities after a period of reaction to obtain a lithium-rich purified solution and fluoroaluminum slag.

(6) Add sodium carbonate to the lithium-rich purification solution (the amount added is 1.3 times the theoretical amount of lithium carbonate produced), precipitate and filter to obtain lithium carbonate. The lithium leaching rate in the water leaching process reaches 98.23%, and the lithium recovery rate in the entire process reaches 92.36%.

(7) Mix the water-washed slag and fluoroaluminum slag to comprehensively recover the valuable elements of fluorine, aluminum and calcium.

Example 5

(1) Ball mill the lithium-containing carbon residue (containing 40% fluorine and 0.43% lithium) to -100 mesh, and then mix it thoroughly with calcium sulfate at a mass ratio of 100:143 and an excess coefficient of 1 to obtain a mixture.

(2) Put the mixture into the roasting furnace. In the air atmosphere, the partial pressure of the gas in the furnace is 1 standard atmosphere. Then the temperature is raised to 800°C at a heating rate of 5°C/min. The roasted material is obtained after roasting for 2 hours.

(3) Grind the roasted material obtained in step (2) to -100 mesh accounting for 85%, add deionized water, soak it in water at a temperature of 70°C for 2 hours according to a liquid-to-solid ratio of 10mL:1g, and then separate the liquid and solid to obtain water. Leaching residue and water leaching liquid.

(4) Evaporate and concentrate the water immersion liquid obtained in step (3) to a concentration factor of 8 times to obtain a lithium-rich concentrated liquid.

(5) Use sodium hydroxide to neutralize the lithium-rich concentrated liquid obtained in step (4), adjust the pH value of the system to 8.5, and filter out impurities after a period of reaction to obtain a lithium-rich purified liquid and fluoroaluminum slag.

(6) Add trisodium phosphate to the lithium-rich purification liquid obtained in step (5) (the amount added is 1.1 times the theoretical amount of trilithium phosphate produced), precipitate and filter to obtain trilithium phosphate, and the lithium leaching rate in the water leaching process Reaching 90.12%, the recovery rate of lithium in the entire process is 93.28%. The phase of the precipitated lithium product is analyzed by XRD, as shown in Figure 7.

(7) Mix the water-washed slag and fluoroaluminum slag to comprehensively recover the valuable elements of fluorine, aluminum and calcium.

It should be understood that the application of the present invention is not limited to the above examples. Those of ordinary skill in the art can make improvements or changes based on the above descriptions. All these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (10)

1. A method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste, comprising the steps of:

(1) Crushing and refining the lithium-containing aluminum electrolysis dangerous solid waste, and then mixing with a calcium source to obtain a mixture;

(2) Roasting the mixture to obtain a roasted material;

(3) Carrying out crushing and refining treatment on the roasting material, and then carrying out water leaching to obtain slurry, wherein the slurry is subjected to liquid-solid separation to obtain water leaching liquid;

(4) Evaporating and concentrating the water extract to obtain a lithium-rich concentrated solution;

(5) Adding alkali to regulate the pH value of the lithium-rich concentrated solution to neutralize and remove impurities, and filtering to obtain a lithium-rich purified solution;

(6) And adding a lithium precipitating agent and alkali into the lithium-rich purifying liquid to neutralize precipitated lithium, and then filtering to obtain lithium salt.

2. The method of preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to claim 1, wherein the method further comprises the steps of:

in the step (3), the slurry is subjected to liquid-solid separation to obtain water immersion liquid and water immersion slag;

washing the water leaching residue for a plurality of times until the washing liquid is neutral, filtering to obtain water washing liquid and water leaching residue, and returning the water washing liquid to the water leaching process of the step (3) for recycling;

in the step (5), the lithium-rich purifying liquid is obtained through filtration, and meanwhile, fluorine aluminum slag is also obtained;

in the step (6), lithium salt is obtained by filtering, and meanwhile lithium precipitation filtrate is also obtained, and the lithium precipitation filtrate is returned to the water leaching process of the step (3) for recycling;

and mixing the water washing slag and the fluorine aluminum slag to comprehensively recover fluorine element, aluminum element and calcium element.

3. The method of preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to claim 1, wherein the lithium-containing aluminum electrolysis hazardous solid waste is selected from one or more of a overhaul slag, a carbon residue, a cathode ash, an aluminum ash, a waste electrolyte;

the granularity of the crushed and refined lithium-containing aluminum electrolysis dangerous solid waste is below-50 meshes;

the calcium source is selected from calcium-containing materials;

the calcium-containing material is one or more selected from calcium oxide, calcium carbonate, calcium sulfate, calcium nitrate, calcium hydroxide, calcium peroxide and calcium hypochlorite.

4. The method of claim 1, wherein the excess factor of the hazardous solid waste for aluminum electrolysis to the calcium source is 1 to 2 based on the stoichiometric ratio required for the added calcium element to form calcium fluoride with the fluorine element in the hazardous solid waste for aluminum electrolysis.

5. The method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to claim 1, wherein in the step (1), the crushed and refined aluminum electrolysis hazardous solid waste and a calcium source are uniformly mixed by ball milling, grinding or a mixer.

6. The method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to claim 1, wherein the parameters of the roasting treatment in the step (2) include: the roasting temperature is 300-1000 ℃, the roasting time is 0.5-8 h, the roasting atmosphere is any one of air, compressed air, oxygen and oxygen-enriched gas, and the roasting pressure is any value in the range of 1-2 standard atmospheric pressures.

7. The method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid wastes according to claim 1, wherein in the step (3), the particle size of the roasted material after the crushing and refining treatment is any particle size ranging from-50 meshes to-400 meshes;

the leaching solution adopted by the water leaching is an aqueous solution, and the aqueous solution is one of an aqueous neutral solution, an acidic aqueous solution and an alkaline aqueous solution;

the parameters of the water immersion include: the ratio of the volume of the leaching solution to the weight of the roasting material subjected to crushing and refining treatment is 2mL:1 g-10 mL:1g, the water leaching time is 0.5-6 h, and the water leaching temperature is 50-90 ℃.

8. The method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to claim 1, wherein in the step (4), the concentration of lithium ions in the lithium-rich concentrated solution is 2-20 g/L.

9. The method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid waste according to claim 1, wherein in the step (5), the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, quicklime and calcium hydroxide, and the pH value of the lithium-rich concentrated solution is adjusted to any value in the range of 7.5-9.5.

10. The method for preferentially extracting lithium from lithium-containing aluminum electrolysis hazardous solid wastes according to claim 1, wherein in the step (6), the lithium precipitating agent is one of sodium carbonate, carbonic acid, trisodium phosphate and phosphoric acid, the alkali is one or more selected from sodium hydroxide, ammonia water and sodium metaaluminate, and the pH value of the filtrate is adjusted to any value in the range of 10-13.