Method for extracting lithium by roasting electrolyte at low temperature

Abstract

The invention discloses a method for extracting lithium by roasting electrolyte at low temperature. The method comprises the following steps: 1, decarbonizing, crushing and sieving lithium-containing electrolytic waste residues of waste electrolyte; 2, fully mixing an electrolyte and an auxiliary material, and carrying out low-temperature roasting; 3, mixing sulfuric acid with water to obtain an acid solution; 4, after the clinker is cooled, adding the acid solution according to a certain proportion to carry out low-temperature leaching, and carrying out filter pressing on a leaching solution to obtain a first filtrate and a first filter residue; and 5, adding sodium carbonate into the first filtrate after lithium precipitation, carrying out a heating reaction by using a constant-temperature water bath kettle, and filtering, washing and drying after the reaction to obtain a finished product lithium carbonate. 6, adding the first filter residue into an acid solution, and performing auxiliary leaching, stirring and filtering by utilizing ultrasonic waves to obtain a second filtrate and a second filter residue; the second filter residue is used for extracting aluminum fluoride after being washed, and the second filtrate can be returned to the size mixing process again for cyclic utilization. According to the method, lithium can be extracted at a high recovery rate, generation of harmful substances such as hydrogen fluoride is effectively reduced, and by-products in the recovery process can be subjected to resource utilization through an innovative technology and process and are converted into products with high additional values, so that the production cost can be obviously reduced.

Description

Technical Field

[0001] The invention relates to a method for extracting lithium from a low-temperature calcined electrolyte. Background Art

[0002] Lithium is an important strategic resource with a relatively low abundance in the earth's crust. Therefore, extracting lithium from waste lithium electrolytes containing lithium electrolytic waste residues can not only reduce environmental pollution, but also effectively recover valuable resources. The lithium content in waste lithium electrolytes containing lithium electrolytic waste residues is usually low, and there are many impurities. The impurity ion concentration of the leaching solution is high and difficult to remove. Harmful byproducts such as hydrogen fluoride will be produced during the lithium extraction process, which brings challenges to the lithium extraction process. Researchers have developed a variety of lithium extraction technologies, including acid leaching, alkaline leaching, aluminum sulfate leaching, aluminum chloride leaching, sodium carbonate extraction, organic acid assisted leaching, sulfuric acid roasting and fluoridation roasting. The lithium extraction process usually includes pretreatment, leaching, separation and purification. Pretreatment usually involves crushing and screening of waste residues, and the leaching process uses chemical reagents to convert lithium into a soluble form. The separation and purification steps further separate lithium from other impurities to finally obtain a high-purity lithium product. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for extracting lithium from a low-temperature calcined electrolyte, aiming to solve the above technical problems.

[0004] To achieve the above object, a method for extracting lithium from a low-temperature calcined electrolyte proposed in the present invention comprises:

[0005] S1. crushing and screening the waste electrolyte containing lithium electrolytic waste residue;

[0006] S2. The electrolyte and auxiliary materials are fully mixed and calcined at low temperature to obtain the calcined material after the calcination is completed.

[0007] S3. Mix sulfuric acid and water to obtain an acid solution.

[0008] S4, adding the roasted clinker from step S2 to the acid solution obtained from step S3. Control the solid-liquid mass ratio to be 1:1.5-1:5 and the temperature to be 50°C-95°C, and perform the leaching reaction while stirring. After the leaching reaction is completed, separate the solid and liquid to obtain a first filtrate and a second filter residue;

[0009] S5. After purifying and precipitating lithium, the first filtrate is added with sodium carbonate and heated in a constant temperature water bath for reaction. After the reaction, the filtrate is filtered, washed and dried to obtain finished lithium carbonate.

[0010] S6. Add an acid solution to the first filter residue, and use ultrasound to assist in leaching, stirring and filtering under certain conditions to obtain a second filtrate and a second filter residue. The second filter residue can be used as a raw material for aluminum fluoride recovery after washing, and the second filtrate can be recycled.

[0011] Preferably, in step S1, the electrolyte is crushed and then sieved through a 80-200 mesh sieve.

[0012] Preferably, before step S1, the electrolyte is decarbonized to reduce the generation of harmful substance hydrogen fluoride and improve the extraction efficiency of lithium.

[0013] Preferably, in step S2, the lithium content in the aluminum electrolyte is 1%-4% (e.g., 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.8%, etc.); and the auxiliary material is calcium oxide and / or calcium hydroxide.

[0014] Preferably, the mass ratio of the auxiliary material to the electrolyte in step S2 is (1:2)-(1:10), for example, 1:3, 1:4, 1:5, 1:7, 1:9, etc.

[0015] Preferably, in step S3, the pH value of the acid solution is less than 5.

[0016] Preferably, in step S4, the leaching time is 1-4 h, for example, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, etc.

[0017] Preferably, in step S5, after lithium precipitation, 1.2 times of sodium carbonate is added to the first filtrate and heated in a constant temperature water bath for reaction.

[0018] Preferably, in step S6, the leaching temperature is between 50°C and 95°C, such as 55°C, 60°C, 65°C, 80°C, 85°C, etc.

[0019] Preferably, in step S6, the leaching time is 1-4 h, such as 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, etc.

[0020] In the technical scheme of the present invention, the waste electrolyte containing lithium electrolytic waste residue is first crushed and screened, and then a decarbonization process is performed to improve the lithium extraction rate of the electrolyte. Then the electrolyte and auxiliary materials are fully mixed and low-temperature roasted. After the clinker is cooled, an acid solution is added in proportion for low-temperature leaching, and the finally obtained washed slag can be used to extract aluminum fluoride. In the first filtrate extracted by the present invention, Li can be enriched to more than 10g / , Ca is about 200mg / L, F is about 10mg / L, and AL is less than 5mg. Compared with the traditional method, the operation is simple, the evaporation concentration process is saved, and energy is saved. In addition, aluminum fluoride can be extracted from the tailings, which significantly reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 Schematic diagram of the process of the novel electrolyte lithium extraction method according to an embodiment of the present invention.

[0023] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0026] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] The invention provides a method for extracting lithium by low-temperature calcining electrolyte.

[0028] like Figure 1 As shown, the low-temperature calcination electrolyte lithium extraction method provided by the embodiment of the present invention comprises the following steps:

[0029] S1. crushing and screening the waste electrolyte containing lithium electrolytic waste residue;

[0030] S2. The electrolyte and auxiliary materials are fully mixed and calcined at low temperature to obtain the calcined material after the calcination is completed.

[0031] S3. Mix sulfuric acid and water to obtain an acid solution.

[0032] S4, adding the roasted clinker from step S2 to the acid solution obtained from step S3. Control the solid-liquid mass ratio to be 1:1.5-1:5, the temperature to be 50°C-95°C, and carry out the leaching reaction while stirring. After the leaching reaction is completed, separate the solid and liquid to obtain the first filtrate and the second filter residue;

[0033] S5. After purifying and precipitating lithium, the first filtrate is added with sodium carbonate and heated in a constant temperature water bath for reaction. After the reaction, the filtrate is filtered, washed and dried to obtain finished lithium carbonate.

[0034] S6. Add an acid solution to the first filter residue, and use ultrasound to assist in leaching, stirring and filtering under certain conditions to obtain a second filtrate and a second filter residue. The second filter residue can be used as a raw material for aluminum fluoride recovery after washing, and the second filtrate can be recycled.

[0035] Preferably, in step S1, the electrolyte is crushed and then sieved through a 80-200 mesh sieve.

[0036] Preferably, before step S1, the electrolyte is decarbonized to reduce the generation of harmful substance hydrogen fluoride and improve the extraction efficiency of lithium.

[0037] Preferably, in step S2, the lithium content in the aluminum electrolyte is 1%-4% (e.g., 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.8%, etc.); and the auxiliary material is calcium oxide and / or calcium hydroxide.

[0038] Preferably, the mass ratio of the auxiliary material to the electrolyte in step S2 is (1:2)-(1:10), for example, 1:3, 1:4, 1:5, 1:7, 1:9, etc.

[0039] Preferably, in step S3, the pH value of the acid solution is less than 5.

[0040] Preferably, in step S4, the leaching time is 1-4 h, for example, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, etc.

[0041] Preferably, in step S5, after lithium precipitation, 1.2 times of sodium carbonate is added to the first filtrate and heated in a constant temperature water bath for reaction.

[0042] Preferably, in step S6, the leaching temperature is between 50°C and 95°C, such as 55°C, 60°C, 65°C, 80°C, 85°C, etc.

[0043] Preferably, in step S6, the leaching time is 1-4 h, such as 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, etc.

[0044] The technical solution of the present invention is further described below by specific examples. Those skilled in the art should understand that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] Example 1

[0046] 1. Crushing and grinding: After decarbonizing the lithium-containing electrolytic waste slag, add it to the crusher for wet ball milling. After the ball mill passes through 80-200 mesh, it is sieved, dried and sieved to finally form a light yellow powder.

[0047] 2. The mass ratio of calcium hydroxide and electrolyte (containing lithium: 2.9315%) is 1:3, at a temperature of 250°C

[0048] Calcination conditions for 1.5h.

[0049] 3. Preparation of acid solution: Use sulfuric acid and distilled water to prepare 5L of acid solution for use. The pH value of the acid solution should be controlled at 4.5-5.

[0050] 4. First acid leaching: 1 kg of roasted clinker was mixed with acid solution (solid-liquid ratio 1:2) and added to a stirring axe. Leaching was performed at a temperature of 60°C and a stirring speed of 250 r / min. The temperature was kept for 1.5 hours, and the filter was pressed for 1.5 hours to obtain a filtrate and a filter residue. The obtained filtrate was purified and impurities were removed to prepare lithium carbonate.

[0051] 5. Second acid leaching: Add the filter residue in step 4) into the acid solution for slurry adjustment (solid-liquid ratio 1:2). Use ultrasonic assisted leaching, at a temperature of 60°C and a stirring speed of 250r / min, use ultrasonic assisted heat preservation leaching for 1.5h. Press filter for 1.5h to obtain filtrate 2 and filter residue 2, and filtrate 2 enters the first leaching cycle for use.

[0052] 6. Purification and impurity removal: add calcium oxide to the filtrate in step 4), adjust the solution system pH to 11, stir for 30 minutes, filter and transport the filtrate to a concentration tank through a pipeline, rinse the filter cake with 500g of pure water and then drain it, transfer the filter cake to a pickling tank at a temperature of 60°C, add an appropriate amount of sulfuric acid, and obtain a pickling slag with extremely low lithium content.

[0053] 7. Concentration: Concentrate the filtrate in step 6)

[0054] 8. Lithium precipitation: Add sodium carbonate (1.2 times the theoretical value) to the concentrated lithium solution in step 7) and heat it in a constant temperature water bath for reaction. After the reaction, filter, wash and dry to obtain lithium carbonate.

[0055] The overall process has a lithium recovery rate of 91% and a fluorine removal rate of 94%, based on the lithium and fluorine contents in the lithium-containing waste electrolyte.

[0056] Example 2

[0057] 1. Crushing and grinding: After decarbonizing the lithium-containing electrolytic waste slag, add it to the crusher for wet ball milling. After the ball mill passes through 80-200 mesh, it is sieved, dried and sieved to finally form a light yellow powder.

[0058] 2. The mass ratio of calcium hydroxide to electrolyte (containing lithium: 2.5745%) is 1:5, and the mixture is calcined at 500°C for 2 hours.

[0059] 3. Preparation of acid solution: Use sulfuric acid and distilled water to prepare 8L of acid solution for use. The pH value of the acid solution should be controlled at 4-4.5.

[0060] 4. First acid leaching: 1 kg of roasted clinker was mixed with acid solution (solid-liquid ratio 1:3) and added to a stirring axe. Leaching was performed at a temperature of 70°C and a stirring speed of 250 r / min. The temperature was kept for 2 hours, and the filter was pressed for 1.5 hours to obtain a filtrate and a filter residue. The obtained filtrate was purified and impurities were removed to prepare lithium carbonate.

[0061] 5. Second acid leaching: Add the filter residue in step 4) into the acid solution for slurry adjustment (solid-liquid ratio 1:3). Use ultrasonic assisted leaching, at a temperature of 70°C and a stirring speed of 250r / min, use ultrasonic assisted heat preservation leaching for 2 hours. Press filter for 1.5 hours to obtain filtrate 2 and filter residue 2, and filtrate 2 enters the first leaching cycle for use.

[0062] 6. Purification and impurity removal: add calcium oxide to the filtrate in step 4), adjust the solution system pH to 11, stir for 40 minutes, filter and transport the filtrate to a concentration tank through a pipeline, rinse the filter cake with 500g of pure water and then drain it, transfer the filter cake to a pickling tank at a temperature of 65°C, add an appropriate amount of sulfuric acid, and obtain a pickling slag with extremely low lithium content.

[0063] 7. Concentration: Concentrate the filtrate in step 6)

[0064] 8. Lithium precipitation: Add sodium carbonate (1.2 times the theoretical value) to the concentrated lithium solution in step 7) and heat it in a constant temperature water bath for reaction. After the reaction, filter, wash and dry to obtain lithium carbonate.

[0065] The overall process has a lithium recovery rate of 92% and a fluorine removal rate of 95%, based on the lithium and fluorine contents in the lithium-containing waste electrolyte.

[0066] Example 3

[0067] 1. Crushing and grinding: After decarbonizing the lithium-containing electrolytic waste slag, add it to the crusher for wet ball milling. After the ball mill passes through 80-200 mesh, it is sieved, dried and sieved to finally form a light yellow powder.

[0068] 2. The mass ratio of calcium hydroxide to electrolyte (containing lithium: 3.1455%) is 1:7 and the mixture is calcined at 700°C for 2 hours.

[0069] 3. Preparation of acid solution: Use sulfuric acid and distilled water to prepare 10L of acid solution for use. The pH value of the acid solution should be controlled at 3-4.

[0070] 4. First acid leaching: 1 kg of roasted clinker was mixed with acid solution (solid-liquid ratio 1:3.5) and added to a stirring axe. Leaching was performed at a temperature of 85°C and a stirring speed of 250 r / min. The temperature was kept for 2 hours, and the filter was pressed for 1.5 hours to obtain a filtrate and a filter residue. The obtained filtrate was purified and impurities were removed to prepare lithium carbonate.

[0071] 5. Second acid leaching: Add the filter residue in step 4) into the acid solution for slurry adjustment (solid-liquid ratio 1:3.5). Use ultrasonic assisted leaching, at a temperature of 85°C and a stirring speed of 250r / min, use ultrasonic assisted heat preservation leaching for 2 hours. Press filter for 1.5 hours to obtain filtrate 2 and filter residue 2, and filtrate 2 enters the first leaching cycle for use.

[0072] 6. Purification and impurity removal: add calcium oxide to the filtrate in step 4), adjust the solution system pH to 11, stir for 50 minutes, filter and transport the filtrate to a concentration tank through a pipeline, rinse the filter cake with 500g of pure water and then drain it, transfer the filter cake to a pickling tank at a temperature of 70°C, add an appropriate amount of sulfuric acid, and obtain a pickling slag with extremely low lithium content.

[0073] 7. Concentration: Concentrate the filtrate in step 6)

[0074] 8. Lithium precipitation: Add sodium carbonate (1.2 times the theoretical value) to the concentrated lithium solution in step 7) and heat it in a constant temperature water bath for reaction. After the reaction, filter, wash and dry to obtain lithium carbonate.

[0075] The overall process has a lithium recovery rate of 92.5% and a fluorine removal rate of 95%, based on the lithium and fluorine contents in the lithium-containing waste electrolyte.

[0076] In summary, the waste electrolyte containing lithium electrolytic waste residue is decarbonized, crushed and sieved; then the electrolyte and auxiliary materials are fully mixed and low-temperature roasted. In the process of lithium extraction, the second filtrate obtained after acid leaching and filter pressing can be returned to the slurry preparation process for recycling. At the same time, the by-product aluminum fluoride obtained in the subsequent process can be sold, and finally the finished lithium carbonate is obtained. In this application, lithium can be extracted at a high recovery rate, and the by-products in the recovery process can be recycled, which can significantly reduce the production cost.

[0077] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A low-temperature calcined electrolyte lithium extraction process, characterized in that: The electrolyte lithium extraction method comprises the following steps: S1. crushing and screening the waste electrolyte containing lithium electrolytic waste residue; S2, the electrolyte and the auxiliary materials are fully mixed and roasted at low temperature, and roasted clinker is obtained after the roasting is completed; S3, mixing sulfuric acid with water to obtain an acid solution; S4, adding the roasted clinker of step S2 to the acid solution obtained in step S3, controlling the solid-liquid mass ratio to be 1:1.5-1:5 and the temperature to be 50°C-95°C, performing leaching reaction while stirring, and separating the solid and liquid after the leaching reaction is completed to obtain a first filtrate and a second filter residue; S5, after purifying and precipitating lithium, the first filtrate is added with sodium carbonate and heated in a constant temperature water bath for reaction, and after the reaction, filtered, washed and dried to obtain finished lithium carbonate; S6. Add an acid solution to the first filter residue, and use ultrasound to assist in leaching, stirring and filtering under certain conditions to obtain a second filtrate and a second filter residue. The second filter residue can be used as a raw material for aluminum fluoride recovery after washing, and the second filtrate can be recycled.

2. The method for extracting lithium from a low-temperature calcined electrolyte according to claim 1, characterized in that: The lithium content of the electrolyte in step S1 is 1%-4%; after being crushed, it is sieved through a 80-200 mesh sieve.

3. The method for extracting lithium from a low-temperature calcined electrolyte according to claim 1, characterized in that: Before step S1, the electrolyte is decarbonized.

4. The method for extracting lithium from a low-temperature calcined electrolyte according to claim 1, characterized in that: In step S2, the mass ratio of auxiliary material to electrolyte is 1:(2-10), and the auxiliary material is calcium hydroxide and / or calcium oxide.

5. The method for extracting lithium from a low-temperature calcined electrolyte according to claim 1, characterized in that: In step S2, the calcination temperature is 300°C-1000°C and the calcination time is 0.5h-3h.

6. The method for extracting lithium from a low-temperature calcined electrolyte according to claim 1, characterized in that: The pH value of the acid solution in step S3 is less than 5.

7. The method for extracting lithium from a low-temperature calcined electrolyte according to claim 1, characterized in that: The leaching time in step S4 is 1-4 hours.

8. The method for extracting lithium from a low temperature calcined electrolyte according to claim 1, characterized in that: In step S5, after lithium precipitation, 1.2 times of sodium carbonate is added to the first filtrate and heated in a constant temperature water bath for reaction.

9. The method for extracting lithium from a low temperature calcined electrolyte according to claim 1, characterized in that: In step S6, the second filtrate and the second filter residue are obtained by stirring the leaching process with the aid of ultrasonic wave at 50° C. to 95° C. for 1 to 4 hours and filtering.

Images