Method for recycling aluminum from aluminum lithium salt mixed solution obtained by acid leaching of aluminum electrolyte waste

Abstract

The invention discloses a method for recycling aluminum from an aluminum lithium salt mixed solution obtained by acid leaching of aluminum electrolyte waste materials, and relates to the technical field of lithium extraction through wet smelting of the aluminum electrolyte waste materials. Comprising the following steps: synergistically leaching an aluminum-lithium salt mixed solution according to the weight ratio parameters of the aluminum electrolyte waste, water, acid and aluminum hydroxide, and controlling the free acid content of a leaching solution in the acid leaching process to be 12-15g / L and the aluminum ion content to be 7-10g / L, so that the lithium content in acid leaching residues is 1t; and 0.05%. According to the method, the concentration of free acid and aluminum ions in the pickle liquor is precisely regulated and controlled, and the pH sectional precipitation technology is combined, so that selective precipitation of aluminum from the mixed liquor is realized, the recovery rate reaches 94.5% or above, the main content of the recovered aluminum hydroxide is greater than or equal to 57%, commodity aluminum hydroxide can be completely replaced, a resource closed loop of leaching, precipitation and recovery is formed, and the method is suitable for industrial production. Meanwhile, the lithium carbonate mother liquor containing lithium is used for adjusting the pH and removing impurities, lithium resources in the mother liquor are synchronously recycled, the comprehensive lithium recycling rate is increased by 2%-3%, and lithium loss caused by aluminum and lithium coprecipitation in a traditional process is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of wet smelting and lithium extraction from aluminum electrolyte waste, and specifically to a method for recovering and reusing aluminum from an aluminum-lithium salt mixed solution obtained by acid leaching of aluminum electrolyte waste. Background Art

[0002] Currently, wet acid leaching of lithium from aluminum electrolyte waste has become the mainstream technology. However, in this process, to increase the lithium leaching rate, an excess of aluminum hydroxide must be added as a co-leaching agent, resulting in a high content of aluminum metal in the leached lithium salt solution. The current common method is to purify the lithium salt solution obtained by acid leaching using a one-step deep purification method. However, this method causes the aluminum element to co-precipitate with various other metal ions, resulting in waste residue that is discarded, resulting in the disadvantage of effectively reusing the aluminum metal element.

[0003] In summary, existing technologies have problems such as the inability to effectively recycle aluminum metal elements, resource waste, and high production costs. The present invention aims to achieve the recycling and reuse of aluminum metal elements, turning waste into treasure, reducing resource waste, and lowering enterprise production costs. Summary of the Invention

[0004] The object of the present invention is to provide a method for recovering and recycling aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for recovering and recycling aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste, comprising the following steps: The aluminum electrolyte waste, water, acid, and aluminum hydroxide are used to synergistically leach a mixed solution of aluminum and lithium salts. The free acid content of the leachate is controlled to be 12-15 g / L and the aluminum ion content is controlled to be 7-10 g / L during the acid leaching process, so that the lithium content in the acid leaching residue is less than 0.05%. An alkaline substance is used to adjust the pH value of the leached slurry to remove fluoride ions and trivalent iron ions, and after filtration, an aluminum-lithium salt mixed solution free of solid matter is obtained; Adding an alkaline substance to the aluminum lithium salt mixed solution, adjusting the pH value to 3.5-5.5 and heating to 60-85° C., stirring and reacting for 70-100 minutes, and then aging to completely convert the ionic aluminum salt into high-purity aluminum hydroxide solid, and recovering the aluminum hydroxide after filtration and separation; The lithium salt solution after dealumination is deeply purified and concentrated to remove sodium salt to produce lithium carbonate product; The recovered aluminum hydroxide is returned to the acid leaching process of aluminum electrolyte waste, and lithium is extracted by synergistic leaching according to the ratio parameters of material, water, acid and aluminum hydroxide, replacing commercial aluminum hydroxide as a leaching agent.

[0006] Preferably, the weight ratio of the aluminum electrolyte waste, water, acid and aluminum hydroxide is 1 / 2.5-3 / 0.25-0.30 / 0.09-0.15, and the water-insoluble lithium content in the acid leaching residue is less than 0.05%.

[0007] Preferably, the alkaline substance is a lithium carbonate precipitation mother liquor containing 15-18 g / L of free alkalinity and 1.1-1.6 g / L of lithium ions. The pH value is adjusted to 2.5-3.0 to remove fluoride ions, trivalent iron ions and some organic impurities. After filtration, a clear aluminum-lithium salt mixed solution is obtained. At this time, when the pH is 3.0, aluminum and lithium do not form a co-precipitation and fluorine and trivalent iron are completely precipitated.

[0008] Preferably, the alkaline substance is one of sodium hydroxide, sodium carbonate or ammonia water. After adjusting the pH value to 3.5-5.5, the temperature is raised to 60-85°C and stirred for reaction. The deep purification of the lithium salt solution includes removing metal ions such as calcium and magnesium. After purification, the sodium salt is removed by concentration to produce lithium carbonate.

[0009] Preferably, when the aluminum hydroxide returns to the acid leaching process, the weight ratio of the material, water, acid and aluminum hydroxide is 1 / 2.5-3 / 0.2-0.35 / 0.09-0.13, replacing commercial aluminum hydroxide for collaborative leaching and lithium extraction.

[0010] Preferably, the acid is hydrochloric acid with a mass fraction of 28%-35%.

[0011] Preferably, the alkaline substance is a lithium carbonate precipitation mother liquor containing 15-18 g / L of free alkali and 1.3-1.6 g / L of lithium ions, the pH value is adjusted to 2.5-3.0, and filtration is performed using a 0.22 μm microporous filter membrane.

[0012] Preferably, the alkaline substance is sodium carbonate, and when the pH is adjusted to 4.5, the particle size D50 of the aluminum hydroxide precipitate is ≥20 μm, and the filtration speed is ≥50 L (m 2 ・h)).

[0013] Preferably, the temperature-raising reaction is carried out in two stages: first, the temperature is raised to 60-70° C., the pH is adjusted, and then the temperature is raised to 80-85° C. for insulation reaction.

[0014] Preferably, the deep purification comprises adding excess sodium carbonate to the lithium salt solution to form carbonate precipitates of calcium and magnesium ions, and the calcium and magnesium ion contents in the filtrate after filtration are both <50 ppm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: A method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste. By precisely controlling the free acid and aluminum ion concentrations in the acid leaching solution and combining it with pH segmented precipitation technology, selective precipitation of aluminum from the mixed solution is achieved, with a recovery rate of over 94.5%. The main content of recovered aluminum hydroxide is ≥57%, which can completely replace commercial aluminum hydroxide, forming a closed loop of leaching, precipitation, and recovery. At the same time, lithium-containing lithium carbonate mother liquor is used to adjust the pH and remove impurities, and lithium resources in the mother liquor are simultaneously recovered. The comprehensive lithium recovery rate is increased by 2%-3%, avoiding lithium loss caused by aluminum and lithium co-precipitation in traditional processes.

[0016] At the same time, lithium carbonate mother liquor is used as a pH regulator to replace traditional caustic soda, reducing alkali consumption by more than 30% and reducing wastewater discharge. Sodium carbonate is preferred as a precipitant, and the aluminum hydroxide precipitation particle D50 is ≥20um, with a filtration speed of 50L (m 2 ・h), significantly shortening the solid-liquid separation time and reducing energy consumption. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like, which indicate orientations or positional relationships, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0020] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0021] Example 1: Aluminum recovery process for scrap with 1.25% lithium content 1. Acid leaching and lithium extraction Take 500g of aluminum electrolyte waste with a lithium content of 1.25%, add 1.5L of water, 0.15L of 31% hydrochloric acid, and 60g of commercial aluminum hydroxide according to the weight ratio of material, water, acid, and aluminum hydroxide = 1 / 3 / 0.3 / 0.12; Stir in a 3L beaker at 400rpm, raise the temperature to 90℃, keep warm and leach for 3 hours, and control the free acid content of the leachate to 13g / L and the aluminum ion content to 8g / L; The acid leaching residue weighed 650 g, the water-insoluble lithium content was 0.048%, and the lithium leaching rate = (6.25 g - 0.2925 g) / 6.25 g × 100% = 95.3%.

[0022] 2. Impurity removal and aluminum precipitation Add lithium carbonate precipitation mother liquor containing 16 g / L free alkali and 1.4 g / L Li+ to the leached slurry, adjust the pH to 3.0, stir for 30 minutes, and filter through a 0.22 μm microporous membrane to obtain 1.6 L of clear aluminum-lithium solution (Al 6.7 g / L, Li 3.8 g / L); Sodium carbonate powder was added to the solution, and the temperature was first raised to 65°C to adjust the pH to 4.5, and then the temperature was raised to 85°C, kept stirring for 90 minutes, aged, and then filtered; 49 g of aluminum hydroxide was recovered (after drying), with an Al content of 20.7%. The recovery rate was (49 g × 20.7%) / (1.6 L × 6.7 g / L) × 100% = 94.5%. The impurity content was: Ca 0.12%, Mg 0.05%, and Li 0.6%.

[0023] 3. Lithium salt solution treatment The dealuminated solution is treated with excess sodium carbonate to remove calcium and magnesium ions (Ca2+ and Mg2+ in the filtrate are both <50 ppm), concentrated by multi-effect evaporation to a Li+ concentration of 20 g / L, and cooled and crystallized to remove NaCl, ultimately producing lithium carbonate with a purity of 99.5%.

[0024] Example 2: Circulation Verification of Recovering Aluminum Hydroxide 1. Soaking ingredients (recycled) Take 500g of the same batch of waste, according to the ratio of material, water, acid, aluminum hydroxide = 1 / 3 / 0.3 / 0.12, add 1.5L of water, 0.15L of hydrochloric acid, and add 49g of aluminum hydroxide recovered in Example 1 (supplemented with 32g of commercial aluminum hydroxide); The leaching conditions were the same as those in Example 1, with the free acid content at 14 g / L and the aluminum ion content at 7.8 g / L. The water-insoluble lithium content of the acid leaching residue is 0.041%, the lithium leaching rate is 95.7%, and the leachate contains Al6.5g / L and Li3.7g / L.

[0025] 2. Secondary recovery of aluminum hydroxide Sodium carbonate was used to adjust the pH to 4.5, and the reaction was carried out at 85°C for 80 minutes. 42.5 g of aluminum hydroxide was recovered, with an Al recovery rate of 96%. The impurity contents were: Ca 0.08%, Mg 0.07%, and Li 1.2%. The Al content in the recovered aluminum hydroxide is close to that in the first recovery, proving the cycle stability.

[0026] Example 3: Aluminum-lithium separation of high-lithium waste 1. Acid leaching and lithium extraction Take 800g of waste material with a lithium content of 1.58%, add 1.25L of water, 0.125L of 35% hydrochloric acid, and 45g of commercial aluminum hydroxide according to the ratio of material, water, acid, and aluminum hydroxide = 1 / 2.5 / 0.25 / 0.09; Leaching at 85℃ for 5 hours, controlling free acid to 12.8g / L and aluminum ion to 8.6g / L; The water-insoluble lithium content of the acid leaching residue is 0.035%, the lithium leaching rate is 97.12%, and the leachate contains Li4.5g / L and Al6.26g / L.

[0027] 2. Staged heating and aluminum deposition First, the temperature was raised to 70℃ and the pH was adjusted to 4.5 with sodium carbonate, then the temperature was raised to 90℃ and kept for 90 minutes. 45.79g of aluminum hydroxide was recovered by filtration, with an Al recovery rate of 95%, a particle size of D50 = 22um, and a filtration speed of 52L (m 2 ・h); After deep purification, the solution is used to produce lithium carbonate (Li2CO3), and the product purity reaches battery grade (total impurity amount <0.1%).

[0028] Comparative example: Traditional one-step purification process After leaching according to the ingredients in Example 1, the pH was directly adjusted to 10 with sodium carbonate to purify the lithium salt solution; Aluminum is co-precipitated with fluorine and iron, the aluminum recovery rate is <10%, and the residual Al in the lithium salt solution is 0.5g / L, requiring an additional aluminum removal process, which increases the production cost by 20%.

[0029] Summary table of features of the embodiments

[0030] Examples 1-3 cover waste materials with lithium contents ranging from 1.25% to 1.58%, verifying the adaptability of the process to raw materials of different grades; After the recovered aluminum hydroxide was recycled twice, the aluminum recovery rate and lithium leaching rate did not show significant attenuation, proving the feasibility of the closed-loop process. Lithium salt solution can be used to prepare lithium carbonate or lithium titanate according to demand, expanding application scenarios; Compared with the traditional one-step method, the aluminum recovery rate of the present invention is increased by more than 80%, and the additional aluminum removal process is reduced.

[0031] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is limited by the accompanying embodiments and their equivalents.

Claims

1. A method for recovering and recycling aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste, characterized in that: The following steps are involved: The aluminum electrolyte waste, water, acid, and aluminum hydroxide are used to synergistically leach a mixed solution of aluminum and lithium salts. The free acid content of the leachate is controlled to be 12-15 g / L and the aluminum ion content is controlled to be 7-10 g / L during the acid leaching process, so that the lithium content in the acid leaching residue is less than 0.05%. An alkaline substance is used to adjust the pH value of the leached slurry to remove fluoride ions and trivalent iron ions, and after filtration, an aluminum-lithium salt mixed solution free of solid matter is obtained; Adding an alkaline substance to the aluminum lithium salt mixed solution, adjusting the pH value to 3.5-5.5 and heating to 60-85° C., stirring and reacting for 70-100 minutes, and then aging to completely convert the ionic aluminum salt into high-purity aluminum hydroxide solid, and recovering the aluminum hydroxide after filtration and separation; The lithium salt solution after dealumination is deeply purified and concentrated to remove sodium salt to produce lithium carbonate product; The recovered aluminum hydroxide is returned to the acid leaching process of aluminum electrolyte waste, and lithium is extracted by synergistic leaching according to the ratio parameters of material, water, acid and aluminum hydroxide, replacing commercial aluminum hydroxide as a leaching agent.

2. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The weight ratio of the aluminum electrolyte waste, water, acid and aluminum hydroxide is 1 / 2.5-3 / 0.25-0.30 / 0.09-0.15, and the water-insoluble lithium content in the acid leaching residue is less than 0.05%.

3. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The alkaline substance is a lithium carbonate precipitation mother liquor containing 15-18 g / L of free alkalinity and 1.1-1.6 g / L of lithium ions. The pH value is adjusted to 2.5-3.0 to remove fluoride ions, trivalent iron ions and some organic impurities. After filtration, a clear aluminum-lithium salt mixed solution is obtained. At this time, when the pH is 3.0, aluminum and lithium do not form a co-precipitation, and fluorine and trivalent iron are completely precipitated.

4. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The alkaline substance is one of sodium hydroxide, sodium carbonate or ammonia water. After adjusting the pH value to 3.5-5.5, the temperature is raised to 60-85°C and stirred for reaction. The deep purification of the lithium salt solution includes removing metal ions such as calcium and magnesium. After purification, the sodium salt is removed by concentration to produce lithium carbonate.

5. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: When the aluminum hydroxide is returned to the acid leaching process, the weight ratio of the material, water, acid and aluminum hydroxide is 1 / 2.5-3 / 0.2-0.35 / 0.09-0.13, and the aluminum hydroxide is used to replace commercial aluminum hydroxide for collaborative leaching and lithium extraction.

6. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The acid is hydrochloric acid with a mass fraction of 28%-35%.

7. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The alkaline substance is a lithium carbonate precipitation mother liquor containing 15-18 g / L of free alkali and 1.1-1.6 g / L of lithium ions, the pH value of which is adjusted to 2.5-3.0, and a 0.22 μm microporous filter membrane is used for filtration.

8. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The alkaline substance is sodium carbonate. When the pH is adjusted to 4.5, the particle size of aluminum hydroxide precipitation D50 is ≥20um, and the filtration speed is ≥50L (m 2 ・h)).

9. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The temperature-raising reaction is carried out in two stages: firstly, the temperature is raised to 60-70°C, the pH is adjusted, and then the temperature is raised to 80-85°C for insulation reaction.

10. The method for recovering and reusing aluminum from a mixed solution of aluminum and lithium salts obtained by acid leaching of aluminum electrolyte waste according to claim 1, characterized in that: The deep purification includes adding excess sodium carbonate to the lithium salt solution to form carbonate precipitates of calcium and magnesium ions, and the calcium and magnesium ion contents in the filtrate after filtration are both <50 ppm.

Images