A method for synergistic recovery and treatment of ternary iron-removal aluminum slag and lithium-rich aluminum electrolyte slag

Abstract

The application provides a method for treating and recycling ternary iron-removing aluminum slag and lithium-rich aluminum electrolyte slag, and belongs to the technical field of lithium resource recycling and utilization, and comprises the following steps: preparing an aluminum sulfate solution; pretreating the lithium-rich aluminum electrolyte slag; heating and dissolving; fluorine-aluminum precipitation; evaporation and concentration; alkali impurity removal; and lithium precipitation.The application uses ternary iron-removing aluminum slag as an aluminum source and adopts an aluminum salt leaching process to treat and recycle the lithium-rich aluminum electrolyte slag, thereby solving the problem of large aluminum salt consumption, recycling the ternary iron-removing aluminum slag and the lithium-rich aluminum electrolyte slag, achieving a fluorine resource utilization rate of more than 95%, and achieving a lithium resource recycling rate of more than 96%. The prepared regenerated cryolite and battery-grade lithium carbonate both meet national standards and industry standards.The application has the advantages of simple operation, low cost, green environmental protection, high recycling rate, high social value and considerable economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium resource recycling, and particularly relates to a method for synergistically recycling ternary iron-removing aluminum slag and lithium-rich aluminum electrolyte slag. BACKGROUND

[0002] In recent years, a large amount of lithium-rich aluminum electrolyte is generated while high-yield electrolytic aluminum is produced. According to statistics, the electrolytic aluminum waste slag contains 1-3% lithium, and the lithium-rich aluminum electrolyte contains a large amount of fluorides. The electrolytic aluminum plant usually adopts the treatment method of landfill or stacking. Under natural conditions, the abandoned lithium-rich aluminum electrolyte is weathered and eroded by rainwater, and the soluble fluorides therein enter the soil and groundwater, seriously damaging the ecological environment and ultimately causing great harm to the human body. Therefore, the treatment method of landfill and stacking not only causes environmental pollution, but also leads to the waste of a large amount of lithium and fluorine resources in the lithium-rich aluminum electrolyte. Therefore, it is of great practical significance to study the extraction of lithium from the lithium-rich aluminum electrolyte.

[0003] At present, a good method for recycling lithium-rich aluminum electrolyte is the wet aluminum salt leaching process, which has low cost, simple steps, high leaching rate, and low acid consumption in the leaching process, but large consumption of aluminum salt. CN113981232A discloses a method for directly leaching and recycling lithium elements in aluminum electrolyte waste slag by aluminum sulfate. The method is to grind and sieve the lithium-containing aluminum electrolyte waste slag, mix it with aluminum sulfate and water for reaction, filter to obtain a filtrate, add sodium carbonate to precipitate lithium, then pass in CO2, and then obtain lithium carbonate through heat decomposition, filtration and drying. Although this method effectively utilizes the lithium in the aluminum electrolyte waste slag, the fluorine in the aluminum electrolyte waste slag is not well recovered and utilized. CN105349786A discloses a method for comprehensive recycling and utilization of lithium-containing aluminum electrolyte. The method is to mix the lithium-containing aluminum electrolyte with water, adjust the pH to less than 2 with inorganic acid, add aluminum salt to obtain a lithium-containing solution, purify the lithium-containing solution after rough lithium precipitation to prepare high-purity lithium carbonate, and wash the residue with water to obtain cryolite product. The cryolite obtained by the method has high impurity content and poor quality; and the cation exchange resin is used for removing impurities from the lithium-containing solution, which has high cost.

[0004] Based on the above problems, it is very important to study a method for synergistically recycling ternary iron-removing aluminum slag and lithium-rich aluminum electrolyte slag, which has high impurity content of cryolite, good quality, high recovery and utilization rate of fluorine, and low cost. SUMMARY

[0005] The present application aims to provide a method for synergistically recycling ternary iron-removing aluminum slag and lithium-rich aluminum electrolyte slag, which solves the technical problems of high impurity content of cryolite, poor quality, high cost of using cation exchange resin to remove impurities from lithium-containing solution, and low recovery and utilization rate of fluorine in the prior art.

[0006] To achieve the above object, the present application provides the following technical solutions:

[0007] The present application provides a method for treating ternary iron-removing aluminum slag and lithium-rich aluminum electrolyte slag, comprising the following steps:

[0008] (1) The ternary iron-removing aluminum slag is acid-dissolved, and the acid solution is reacted with sodium carbonate to obtain an aluminum sulfate solution;

[0009] The lithium-rich aluminum electrolyte slag is crushed and then acid-washed to remove impurities to obtain pretreated lithium-rich aluminum electrolyte slag;

[0010] (2) The aluminum sulfate solution and the pretreated lithium-rich aluminum electrolyte slag are heated and dissolved to obtain a dissolution solution;

[0011] (3) The dissolution solution in step (2), ammonium fluoride and sodium sulfate are reacted to obtain a reaction solution, and the reaction solution is filtered to obtain a fluorine-sinking aluminum solution and cryolite;

[0012] (4) The obtained fluorine-sinking aluminum solution is sequentially subjected to evaporation concentration and alkali impurity removal to obtain an impurity-removed solution, and the impurity-removed solution is reacted with a soda solution to obtain lithium carbonate.

[0013] Further, in step (1), the acid used for acid-dissolution is concentrated sulfuric acid; the pH value of the acid solution is 1-1.5, and the concentration of sulfate ions in the acid solution is ≥50 g / L;

[0014] The pH value in the reaction process is 1.5-2.5, the reaction temperature is ≥90℃, and the reaction time is 3-5h.

[0015] Further, in step (1), the particle size of the pretreated lithium-rich aluminum electrolyte slag is ≥100 mesh;

[0016] The liquid-solid ratio of the acid-washing impurity removal is 3-8:1, the acid used for the acid-washing impurity removal is dilute sulfuric acid, the pH value in the acid-washing impurity removal process is 1-2.7, and the acid-washing impurity removal time is 1-5h.

[0017] Further, in step (2), the heating and dissolving temperature is 50-80℃, and the time is 1-4h;

[0018] The molar ratio of fluorine to aluminum in the dissolution solution is 1-3:1, and the mass ratio of the aluminum sulfate solution to the lithium-rich aluminum electrolyte slag is 5-10:1.

[0019] Further, in step (3), the molar ratio of fluorine to aluminum in the reaction solution is 3-6:1, and the molar ratio of sodium to aluminum is 3-4.5:1;

[0020] The reaction temperature is 20-30℃, and the reaction time is 1-3h;

[0021] The pH value of the reaction is 4-8.5.

[0022] Further, in step (4), the evaporation concentration is carried out at a temperature of 90-100 DEG C for 0.5-2 hours. + The concentration of the soda solution is 210-240 g / L.

[0023] The concentration of the soda solution is 210-240 g / L.

[0024] Further, in step (4), the evaporation concentration is carried out at a temperature of 90-100 DEG C for 0.5-2 hours.

[0025] Further, in step (4), the evaporation concentration is carried out at a temperature of 90-100 DEG C for 0.5-2 hours. 2- ) : n(Li + ) = 0.5-1:1; wherein n(CO3 2- ) is the molar amount of CO3 2- in the soda solution, and n(Li + ) is the molar amount of lithium in the impurity-removing solution.

[0026] Advantages of the present application:

[0027] (1) The present application uses ternary iron-removing aluminum slag as an aluminum source and adopts an aluminum salt leaching process to recover and treat lithium-rich aluminum electrolytic slag, which not only solves the problem of large consumption of aluminum salt, but also recovers and treats ternary iron-removing aluminum slag and lithium-rich aluminum electrolytic slag, so that resources are maximally utilized.

[0028] (2) The present application does not produce toxic and harmful gases in the treatment process, the fluorine resource utilization rate of the lithium-rich aluminum electrolytic slag is more than 95%, and the quality of the regenerated cryolite meets the national standard requirements.

[0029] (3) The lithium recovery rate of the present application can reach more than 96%, and the quality of lithium carbonate reaches the battery-grade lithium carbonate industry standard. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a process flow chart for the collaborative recovery and treatment of ternary iron-removing aluminum slag and lithium-rich aluminum electrolytic slag.

[0031] Figure 2 It is an XRD graph of the lithium-rich aluminum electrolytic slag of Example 1.

[0032] Figure 3 It is an XRD graph of the cryolite prepared in Example 1. DETAILED DESCRIPTION

[0033] The present application provides a method for collaborative recovery and treatment of ternary iron-removing aluminum slag and lithium-rich aluminum electrolytic slag, comprising the following steps:

[0034] (1) acid-dissolving the ternary iron-removing aluminum slag, and reacting the acid solution with sodium carbonate to obtain an aluminum sulfate solution;

[0035] The lithium-rich aluminum electrolysis slag is crushed and then acid-washed to remove impurities to obtain pretreated lithium-rich aluminum electrolysis slag;

[0036] (2) heating and dissolving the aluminum sulfate solution and the pretreated lithium-rich aluminum electrolysis slag to obtain a dissolution solution;

[0037] (3) reacting the dissolution solution in step (2), ammonium fluoride and sodium sulfate to obtain a reaction solution, and filtering the reaction solution to obtain a fluorine-precipitated aluminum solution and cryolite;

[0038] (4) sequentially subjecting the obtained fluorine-precipitated aluminum solution to evaporation concentration and alkali impurity removal to obtain an impurity-removed solution, and reacting the impurity-removed solution with a soda solution to obtain lithium carbonate.

[0039] In the present application, in step (1), the acid used for acid-dissolution is concentrated sulfuric acid; the pH value of the acid solution is 1-1.5, preferably 1.1-1.4, and further preferably 1.2-1.3; the concentration of sulfate ions in the acid solution is ≥50 g / L, preferably ≥60 g / L, and further preferably ≥70 g / L.

[0040] In the present application, in step (1), the pH value during the reaction is 1.5-2.5, preferably 1.6-2.3, and further preferably 1.8-2.2; the reaction temperature is ≥90℃, preferably 92-110℃, and further preferably 95-105℃; and the reaction time is 3-5 h, preferably 3.5-4.5 h, and further preferably 4 h.

[0041] In the present application, in step (1), the particle size of the pretreated lithium-rich aluminum electrolysis slag is ≥100 mesh, preferably ≥115 mesh, and further preferably ≥120 mesh.

[0042] The liquid-solid ratio of the acid-washing impurity removal is 3-8:1, preferably 4-7:1, and further preferably 5-6:1; the acid used for the acid-washing impurity removal is dilute sulfuric acid; the pH value during the acid-washing impurity removal is 1-2.7, preferably 1.3-2.5, and further preferably 1.5-2.2; and the acid-washing impurity removal time is 1-5 h, preferably 1.5-4.5 h, and further preferably 2-4 h.

[0043] In the present application, in step (2), the heating and dissolving temperature is 50-80℃, preferably 55-75℃, and further preferably 60-70℃; and the time is 1-4 h, preferably 1.5-3.5 h, and further preferably 2-3 h.

[0044] In the present application, in step (2), the molar ratio of fluorine to aluminum in the dissolving solution is 1-3:1, preferably 1.2-2.8:1, and further preferably 1.5-2.5:1; the mass ratio of the aluminum sulfate solution to the pretreated lithium-rich aluminum electrolysis residue is 5-10:1, preferably 5.5-9.5:1, and further preferably 6-9:1.

[0045] In the present application, in step (3), the molar ratio of fluorine to aluminum in the reaction solution is 3-6:1, preferably 3.2-5.8:1, and further preferably 3.5-5.5:1; the molar ratio of sodium to aluminum is 3-4.5:1, preferably 3.1-4.3:1, and further preferably 3.3-4.1:1.

[0046] In the present application, in step (3), the reaction temperature is 20-30℃, preferably 22-28℃, and further preferably 24-26℃; the reaction time is 1-3h, preferably 1.5-2.5h, and further preferably 2h; and the pH value during the reaction is 4-8.5, preferably 4.2-8, and further preferably 4.5-7.5.

[0047] In the present application, in step (4), the concentration of lithium in the concentrated solution obtained by evaporation and concentration is ≥20g / L, preferably ≥22g / L, and further preferably ≥25g / L. +

[0048] The concentration of the soda solution is 210-240g / L, preferably 215-235g / L, and further preferably 220-230g / L.

[0049] In the present application, in step (4), the reaction temperature is 90-100℃, preferably 92-98℃, and further preferably 94-96℃; the reaction time is 0.5-2h, preferably 0.7-1.8h, and further preferably 0.9-1.5h.

[0050] In the present application, in step (4), the amount of the soda solution added satisfies n(CO3 2- ) : n(Li + ) = 0.5-1:1, preferably 0.55-0.9:1, and further preferably 0.6-0.7:1; wherein n(CO3 2- ) is the molar amount of CO3 2- in the soda solution, and n(Li + ) is the molar amount of lithium in the impurity-removing solution.

[0051] In the present application, in the preparation of the aluminum sulfate solution, the ternary iron-removing aluminum residue is first acid-dissolved, and the filtered acid solution is then added with sodium carbonate to remove iron ions in the solution by the jarosite method, so that iron is removed at a low pH value, and the loss of aluminum is reduced.​

[0052] Al(OH)3 + 3H + == Al 3+ + 3H2O

[0053] Fe(OH)3 + 3H + == Fe 3+ + 3H2O

[0054] 6Fe 3+ + 2Na + + 4SO4 2- + 12H2O == Na2Fe6(SO4)4(OH) 12 + 12H +

[0055] In the application, the lithium-rich aluminum electrolyte slag is ground and crushed, sieved, and the undersize is pickled to remove impurities:

[0056] 2Al2O3 + 6H + == 2Al 3+ + 3H2O

[0057] 2Fe2O3 + 6H + == 2Fe 3+ + 3H2O

[0058] Al2O3 and Fe2O3 are impurities in the lithium-rich aluminum electrolyte slag.

[0059] In the application, the aluminum sulfate solution is heated and dissolved with the pretreated lithium-rich aluminum electrolyte slag, and a dissolution solution is obtained by filtering:

[0060] Na3AlF6 == 3Na + + AlF n 3-n + (6-n)F -

[0061] Na3AlF6 is a component in the lithium-rich aluminum electrolyte slag.

[0062] In the application, the dissolution solution, ammonium fluoride and sodium sulfate are reacted to obtain a reaction solution, the reaction solution is filtered to obtain a fluorine-saturated aluminum solution and cryolite, and the cryolite is washed and dried to obtain qualified cryolite products.

[0063] 3Na + + AlF n 3-n + (6-n)F - == Na3AlF6

[0064] ​In the present application, the obtained fluorine-saturated aluminum liquid is evaporated and concentrated to obtain a concentrated solution, and then the concentrated solution is added with liquid alkali (mass fraction of liquid alkali is 32%) to adjust pH≥12 to remove impurities to obtain a de-impurity solution;

[0065] M n+ +nOH - ==M(OH) n (M represents a metal ion)

[0066] In the present application, the obtained de-impurity solution is added with soda solution, and reacts at 90-100℃ for 0.5-2h, and after the reaction is completed, lithium carbonate is obtained through centrifugation, washing and drying.

[0067] 2Li + +CO3 2- ==Li2CO3

[0068] The technical solutions provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0069] The ternary iron-removing aluminum slag used in the examples is from Jiangxi Gengfeng Recycling Technology Co., Ltd.

[0070] Example 1

[0071] (1) 1 kg of ternary iron-removing aluminum slag is slurried with water at a liquid-solid ratio of 6:1, concentrated sulfuric acid is added to adjust the pH value to 1.5, the concentration of sulfate ions in the solution is 71 g / L, then filtered, and sodium carbonate is added to the filtered filtrate to maintain the reaction pH value at 1.9, and the reaction is carried out at 95℃ for 4h, and aluminum sulfate solution is obtained by filtration;

[0072] The lithium-rich aluminum electrolyte slag is ground and sieved to a particle size of less than 100 mesh, 1 kg of the undersize material is slurried with water at a liquid-solid ratio of 3:1, 5% dilute sulfuric acid is added to maintain the system pH value at 1.5, and the acid washing is carried out for 1h, and then the filter residue is obtained by filtration;

[0073] (2) The aluminum sulfate solution is diluted from Al content of 27 g / L to Al content of 15 g / L, 8L of the diluted aluminum sulfate solution is taken and reacted with all the acid-washed lithium-rich aluminum electrolyte slag at 60℃ for 2.5h, and the dissolved solution is obtained by filtration, wherein the molar ratio of fluorine to aluminum is 2.7:1;

[0074] (3) The solution in step (2), 857g of ammonium fluoride and 800g of anhydrous sodium sulfate were reacted at 25°C for 2h to obtain a reaction solution. The pH value during the reaction process was 5.5. The molar ratio of fluorine to aluminum in the reaction solution was 5.57:1, and the molar ratio of sodium to aluminum was 3.06:1. The reaction solution was filtered to obtain fluorine-aluminum precipitate liquid and fluorine-aluminum precipitate residue. The fluorine-aluminum precipitate residue was washed in multiple stages with a low concentration of 1g / L ammonium fluoride solution under weakly alkaline conditions with a pH of 8, and dried at 450°C for 3h to obtain 1.6kg of cryolite (sodium hexafluoroaluminate).

[0075] (4) The aluminum fluoride precipitate solution was evaporated and concentrated from 4.2 L to 0.9 L, wherein the concentrated solution contained Li + The concentration was 25.5 g / L. Liquid alkali was added dropwise to adjust the pH to ≥12, and the solution was filtered to obtain the purified solution (lithium sulfate purified solution).

[0076] (5) Add 865 mL of 240 g / L sodium carbonate solution dropwise to the impurity removal solution at a rate of 20 mL / min, wherein n(CO3) 2- ):n(Li + The ratio of fluorine to lithium carbonate was 0.6:1. The mixture was reacted at 90℃ for 1 hour. After the reaction was complete, the mixture was centrifuged at 1000 r / min, washed with pure water, and finally dried at 120℃ for 4 hours to obtain 96.9 g of battery-grade lithium carbonate. The recovery rate of fluorine was 99.3% and the recovery rate of lithium was 97.8%.

[0077] Figure 2 The image shows the XRD pattern of the lithium-rich aluminum electrolyte slag from Example 1. Figure 2 It can be seen that this lithium-rich aluminum electrolyte slag is a mixture with complex peak shapes. By comparing it with the standard card of the substance, it can be determined that its components include KF, LiF, LiNa2AlF6, Na3AlF6 and Al2O3. Figure 3 The image shows the XRD pattern of cryolite prepared in Example 1. Figure 3 It can be seen that the peak shape of the prepared cryolite matches the characteristic peak of Na3AlF6, indicating high purity.

[0078] Example 2

[0079] The difference between Example 2 and Example 1 is that in step (2), the aluminum sulfate solution is diluted to an Al content of 20 g / L, and the solution, 1162 g of ammonium fluoride and 1125 g of anhydrous sodium sulfate from step (2) are reacted.

[0080] 1.9 kg of cryolite (sodium hexafluoroaluminate) and 96.5 g of battery-grade lithium carbonate were obtained, with a fluorine recovery rate of 99.6% and a lithium recovery rate of 96.5%.

[0081] Example 3

[0082] The difference between the embodiment 3 and the embodiment 2 is only that in the step (2), 6L of the diluted aluminum sulfate solution is reacted with the lithium-rich aluminum electrolyte residue after impurity removal by 5% dilute sulfuric acid at 60 DEG C for 2.5h.

[0083] The 1.6kg of cryolite (sodium hexafluoroaluminate) and 97g of battery-grade lithium carbonate are prepared, wherein the recovery rate of fluorine is 99.1%, and the recovery rate of lithium is 97.4%.

[0084] The chemical compositions and element contents of the lithium-rich aluminum electrolyte and the cryolite are shown in Table 1.

[0085] Table 1 Element composition table of lithium-rich aluminum electrolyte and cryolite

[0086]

[0087] The chemical composition of the lithium carbonate is shown in Table 2.

[0088] Table 2 Chemical composition table of lithium carbonate

[0089]

[0090]

[0091] It can be seen from the above embodiments that the application provides a method for synergistically recycling ternary iron-removing aluminum residue and lithium-rich aluminum electrolyte residue, the ternary iron-removing aluminum residue is used as an aluminum source, and the aluminum salt leaching process is used to recycle and process the lithium-rich aluminum electrolyte residue, so that the problem of large consumption of aluminum salt is solved, and the ternary iron-removing aluminum residue and the lithium-rich aluminum electrolyte residue are recycled and processed, and resources are maximally utilized; no toxic and harmful gas is generated in the processing process, the fluorine resource utilization rate of the lithium-rich aluminum electrolyte residue is more than 95%, and the quality of the regenerated cryolite meets the national standard requirements; the lithium recovery rate of the application can be more than 96%, and the quality of the lithium carbonate meets the industry standard of battery-grade lithium carbonate.

[0092] The above only describes the preferred embodiments of the application, and it should be noted that, for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A method for synergistic recovery treatment of ternary iron-removal aluminum slag and lithium-rich aluminum electrolyte slag, characterized in that, The method comprises the following steps: (1) acid-dissolving the ternary iron-removing aluminum slag, and reacting the acid solution with sodium carbonate to obtain an aluminum sulfate solution; The lithium-rich aluminum electrolysis slag is crushed and then subjected to acid pickling to remove impurities, thereby obtaining pretreated lithium-rich aluminum electrolysis slag; In step (1), the acid used for the acid-dissolving is concentrated sulfuric acid; the pH value of the acid solution is 1-1.5, and the concentration of sulfate ions in the acid solution is ≥50 g / L; During the reaction, the pH value is 1.5-2.5, the reaction temperature is ≥90 °C, and the reaction time is 3-5 h; (2) heating and dissolving the aluminum sulfate solution and the pretreated lithium-rich aluminum electrolysis slag to obtain a dissolution solution; (3) reacting the dissolution solution in step (2), ammonium fluoride and sodium sulfate to obtain a reaction solution, and filtering the reaction solution to obtain a fluorine-precipitated aluminum solution and cryolite; In step (3), the molar ratio of fluorine to aluminum in the reaction solution is 3-6:1, and the molar ratio of sodium to aluminum is 3-4.5:1; The reaction temperature is 20-30 °C, and the reaction time is 1-3 h; During the reaction, the pH value is 4-8.5; (4) evaporating and concentrating the fluorine-precipitated aluminum solution to obtain a concentrated solution, adding liquid alkali to the concentrated solution, adjusting the pH value to ≥12 to remove impurities to obtain a removal solution, and reacting the removal solution with a pure alkali solution to obtain lithium carbonate.

2. The method of claim 1, wherein, In step (1), the particle size of the pretreated lithium-rich aluminum electrolysis slag is ≥100 mesh; The liquid-solid ratio of the acid pickling is 3-8:1, the acid used for the acid pickling is dilute sulfuric acid, the pH value during the acid pickling is 1-2.7, and the acid pickling time is 1-5 h.

3. The method of claim 2, wherein, In step (2), the heating and dissolving temperature is 50-80 °C, and the time is 1-4 h; The molar ratio of fluorine to aluminum in the dissolution solution is 1-3:1, and the mass ratio of the aluminum sulfate solution to the pretreated lithium-rich aluminum electrolysis slag is 5-10:

1.

4. The method of claim 3, wherein, In step (4), the evaporation concentration is carried out to obtain a concentrated solution, wherein the concentration of Li + ≥ 20 g / L; The concentration of the pure alkali solution is 210-240 g / L.

5. The method of claim 4, wherein, In step (4), the reaction temperature is 90-100 °C, and the reaction time is 0.5-2 h.

6. The method according to any one of claims 1 to 5, characterized in that, In step (4), the amount of the soda solution added satisfies: n(CO3 2- ) : n(Li + ) = 0.5-1:1; wherein n(CO3 2- ) is the molar amount of CO3 2- in the soda solution, and n(Li + ) is the molar amount of lithium in the impurity-removing solution.

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