Method for preparing lithium salt from ultrafine lepidolite

Abstract

The invention provides a method for preparing lithium salt from superfine lepidolite, and relates to the technical field of extraction of lithium from lepidolite. The method comprises the following steps: step 1, adding superfine lepidolite into a mixed solution containing sodium carbonate and sodium chloride, stirring and autoclaving, completing solid-liquid separation before cooling to 70 DEG C, and collecting filter residues; 2, drying filter residues, adding calcium sulfate and sodium sulfate, uniformly mixing, roasting, and collecting a roasted material; 3, adding water into the roasted material for leaching, and filtering and deslagging a solid-liquid mixture after reaction to obtain a filtrate which is a lithium-containing leaching solution; step 4, adding a saturated sodium carbonate solution into the lithium-containing leaching solution at room temperature until no precipitate is generated, filtering, and collecting filtrate; and 5, concentrating the filtrate, heating, adding a saturated sodium carbonate solution, stirring for reaction, filtering while the solution is hot, and collecting a high-purity lithium carbonate product. The method is short in process and low in cost, can effectively improve the purity and the yield of the lithium carbonate product, and has good economic benefits and social benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of extracting lithium from lepidolite, and particularly relates to a method for preparing lithium salt from superfine particle grade lepidolite. BACKGROUND

[0002] Lepidolite is an important mineral resource, which contains rich rare metal materials such as lithium, sodium, potassium, rubidium, cesium and aluminum. With the increasing energy shortage in the world, developing and utilizing new energy is a common task for the world. As one of the important industries of new energy development, lithium battery new energy is more and more valued by various countries. Therefore, the comprehensive development and application of lepidolite raw materials have become a hot topic today. Lithium and its salts are basic materials of lithium battery new energy, which are praised by scientists as "industrial monosodium glutamate, energy star", are the best materials for producing lithium ion batteries, and are important metals for developing new energy and new materials. Lithium salts produced on a large scale include lithium carbonate, lithium hydroxide monohydrate, lithium chloride, lithium fluoride, lithium sulfide, lithium dihydrogen phosphate and lithium hexafluorophosphate. Among them, lithium carbonate, lithium hydroxide monohydrate and lithium chloride are ranked in the top three in terms of production scale, can be converted into each other, and are also basic materials for preparing other lithium salts.

[0003] At present, the methods for extracting lithium from lepidolite mainly include sulfuric acid method, limestone method, pressure cooking method, hydrochloric acid method, double salt method and one-step chlorination roasting method. The limestone method is the earliest one, but has been gradually eliminated due to large material flow, high energy consumption and low yield. The sulfuric acid leaching method is a relatively widely used industrial production method. The main shortcomings of the sulfuric acid method are: long leaching time, more than 8 hours, high energy consumption and low production efficiency; during leaching, hydrogen fluoride volatilizes, which seriously corrodes the equipment and is not friendly to the environment. Therefore, developing a method for extracting lithium from lepidolite to prepare lithium salt has become a research topic in the industry. SUMMARY

[0004] In order to solve the problems of many defects existing in the limestone method and the sulfuric acid method commonly used for preparing lithium salt from lepidolite, the present application provides a method for preparing lithium salt from superfine particle grade lepidolite. The superfine particle grade lepidolite is used as raw material, fluorine is removed after steaming and cooking, then lithium-containing brine is obtained by roasting and leaching, and lithium salt is prepared after impurity removal and purification.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: A method for preparing lithium salt from superfine particle grade lepidolite, comprising the following steps: Step one, superfine particle grade lepidolite is added to a mixed solution containing sodium carbonate and sodium chloride, and is stirred and cooked, and solid-liquid separation is completed before cooling to 70 DEG C, and the filter residue is collected; Step two, the filter residue collected in step one is dried, then calcium sulfate and sodium sulfate are added, the mixture is uniformly mixed and then is roasted, and the roasted material is collected; Step three, adding proper amount of water to the roasting material collected in step two for leaching, filtering the obtained solid-liquid mixture to remove residue, and obtaining a lithium-containing leaching solution; Step four, adding saturated sodium carbonate solution to the lithium-containing leaching solution collected in step three until no precipitate is generated, filtering, and collecting the filtrate; Step five, concentrating the filtrate collected in step four, then heating and adding saturated sodium carbonate solution, stirring and reacting, and filtering while hot to obtain a lithium carbonate product.

[0006] In the implementation of the above embodiment, preferably, the particle size of the superfine particle grade lepidolite in step one is 200-600 mesh.

[0007] In the implementation of the above embodiment, preferably, the liquid-solid mass ratio of the mixed solution to the superfine particle grade lepidolite in step one is (1.5-3):1; the concentration of sodium carbonate in the mixed solution is 1-5 mol / L, and the concentration of sodium chloride is 0.5-1.5 mol / L.

[0008] In the implementation of the above embodiment, preferably, the stirring and autoclaving conditions in step one are a pressure of 3-5 Mpa, a temperature of 110-200℃, and a time of 1.5-3h.

[0009] In the implementation of the above embodiment, preferably, the mass ratio of sodium sulfate: calcium sulfate: filter residue in step two is (2-4):(3-5):10.

[0010] In the implementation of the above embodiment, preferably, the roasting temperature in step two is 800-1100℃, and the roasting time is 0.5-4h.

[0011] In the implementation of the above embodiment, preferably, the liquid-solid mass ratio of the water to the roasting material in step three is (2-8):1, and the leaching time is 2-3h.

[0012] In the implementation of the above embodiment, preferably, the filtrate collected in step five is concentrated to a lithium ion concentration of 25-35g / L.

[0013] In the implementation of the above embodiment, preferably, after concentration in step five, the solution is heated to 85-95℃ and stirred and reacted for 20-40min.

[0014] In the implementation of the above embodiment, preferably, filtering while hot in step five means that the temperature of the solution during filtering is 50-70℃.

[0015] Compared with the prior art, the beneficial features of the present application are: 1. The method for preparing lithium salt from superfine particle size lepidolite, first, the lepidolite is mixed with sodium carbonate and sodium chloride for pressure boiling, the chloride ion of sodium chloride is used to destroy the stable ore structure of lepidolite, so that the lithium and fluorine elements in the ore are in a weakly bound or free state, under the condition of high temperature pressure boiling, the fluorine enters the solution in the form of ions, and the soluble lithium salt reacts with the carbonate ions in the sodium carbonate to form lithium carbonate precipitate through the common ion effect, so that most of the soluble lithium elements enter the defluorination residue. And the superfine particle size of lepidolite can improve the lithium extraction efficiency of lepidolite and reduce the loss of lithium elements.

[0016] 2. The method for preparing lithium salt from superfine particle size lepidolite, under the condition of roasting, sodium and calcium ions will preferentially replace the lithium elements in the silicate, and then react with K, Rb and Cs elements, reasonable control of the amount of sodium sulfate and calcium during mixing and the roasting condition can improve the selectivity of the reaction and reduce the content of potassium, rubidium and cesium in the lithium-containing leaching solution.

[0017] 3. The method for preparing lithium salt from superfine particle size lepidolite, the addition of sodium carbonate in step four can effectively remove the excess calcium ions.

[0018] 4. The method for preparing lithium salt from superfine particle size lepidolite, the process treatment method is simple, the energy consumption is low, the impurity elements in the lepidolite are removed through appropriate steps, the process is feasible, the purity of the prepared lithium carbonate is above 99.0%, and the total yield of lithium is above 87%. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] The superfine lepidolite used in the embodiments of the present application is produced in Yichun City, Jiangxi Province, and its main chemical components are shown in Table 1: Table 1 Composition table of superfine lepidolite Embodiment 1

[0021] A method for preparing lithium salt from superfine particle size lepidolite, the steps include: Step one, the particle size of 200 purposes of superfine lithium mica is added to the mixed solution containing sodium carbonate and sodium chloride with the liquid-solid mass ratio of 1.5:1, wherein the concentration of sodium carbonate in the mixed solution is 1 mol / L, and the concentration of sodium chloride is 0.5 mol / L. Stirring pressure cooking is carried out under the conditions of 3Mpa pressure and 110℃ temperature for 1.5h. After the pressure cooking reaction is completed, solid-liquid separation is completed before cooling to 70℃, the filter residue is collected, and the filter residue defluorination rate is 95.25%.

[0022] Step two, the filter residue collected in step one is dried and then calcium sulfate and sodium sulfate are added, wherein the mass ratio of sodium sulfate: calcium sulfate: filter residue is 2:3:10, and the mixture is uniformly mixed and then calcined, the calcination temperature is 800℃, the calcination time is 4h, and the calcined material is collected.

[0023] Step three, water is added to the calcined material collected in step two for leaching, wherein the liquid-solid mass ratio of water to calcined material is 2:1, and the leaching time is 2h. After sufficient reaction, the obtained solid-liquid mixture is filtered to remove residue, and the filtrate is obtained as a lithium-containing leaching solution; Step four, under room temperature conditions, saturated sodium carbonate solution is added to the lithium-containing leaching solution collected in step three until no precipitate is generated, and then the solution is filtered to collect the filtrate; Step five, the filtrate collected in step four is evaporated and concentrated to a lithium ion concentration of 25g / L, and then the solution is heated to 85℃, saturated sodium carbonate solution is added to the solution and stirred for 20min. After that, the solution is cooled to 50-70℃ and then filtered, and the filter residue is collected, which is a high-purity lithium carbonate product. The lithium carbonate product is detected to have a lithium carbonate purity of 99.3% and a lithium element yield of 87.1%. Example 2

[0024] A method for preparing lithium salt from superfine lithium mica, the steps comprising: Step one, the particle size of 220 purposes of superfine lithium mica is added to the mixed solution containing sodium carbonate and sodium chloride with the liquid-solid mass ratio of 1.8:1, wherein the concentration of sodium carbonate in the mixed solution is 2 mol / L, and the concentration of sodium chloride is 0.7 mol / L; stirring pressure cooking is carried out under the conditions of 3.5Mpa pressure and 140℃ temperature for 3h, and solid-liquid separation is completed before cooling to 70℃, the filter residue is collected, and the filter residue defluorination rate is 94.97%; Step two, the filter residue collected in step one is dried and then calcium sulfate and sodium sulfate are added, wherein the mass ratio of sodium sulfate: calcium sulfate: filter residue is 2.5:3.5:10, and the mixture is uniformly mixed and then calcined, the calcination temperature is 900℃, the calcination time is 3h, and the calcined material is collected; Step three, water is added to the calcined material collected in step two for leaching with the liquid-solid mass ratio of 4:1, and the leaching time is 2.2h. After sufficient reaction, the obtained solid-liquid mixture is filtered to remove residue, and the filtrate is obtained as a lithium-containing leaching solution; Step four, the lithium-containing leaching solution collected in step three is added with saturated sodium carbonate solution at room temperature until no precipitate is formed, filtered, and the filtrate is collected; Step five, the filtrate collected in step four is concentrated to a lithium ion concentration of 28 g / L, the solution is heated to 95°C, saturated sodium carbonate solution is added to the solution, stirred for 40 min, and filtered at a temperature of 50-70°C during cooling of the solution, and the filter residue is collected, which is a high-purity lithium carbonate product. The purity of lithium carbonate is 99.8%, and the lithium element yield is 87.5%. Example 3

[0025] A method for preparing lithium salt from superfine particle size lepidolite, the steps comprising: Step one, superfine particle size lepidolite with a particle size of less than 280 mesh is added to a mixed solution containing sodium carbonate and sodium chloride at a liquid-solid mass ratio of 2:1, wherein the concentration of sodium carbonate in the mixed solution is 3 mol / L, and the concentration of sodium chloride is 1 mol / L; pressure is 4 Mpa, temperature is 160°C, and stirring pressure is cooked for 2 h; solid-liquid separation is completed before cooling to 70°C, the filter residue is collected, and the defluorination rate of the filter residue is 95.11%; Step two, after the filter residue collected in step one is dried, calcium sulfate and sodium sulfate are added, the mass ratio of sodium sulfate: calcium sulfate: filter residue is 3:4:10, the mixture is uniformly mixed and calcined, the calcination temperature is 1000°C, the calcination time is 2 h, and the calcined material is collected; Step three, the calcined material collected in step two is added with water for leaching at a liquid-solid mass ratio of 6:1, the leaching time is 2.5 h, and after sufficient reaction, the solid-liquid mixture is obtained, the residue is removed by filtration, and the filtrate is a lithium-containing leaching solution; Step four, the lithium-containing leaching solution collected in step three is added with saturated sodium carbonate solution at room temperature until no precipitate is formed, filtered, and the filtrate is collected; Step five, the filtrate collected in step four is concentrated to a lithium ion concentration of 30 g / L, the solution is heated to 90°C, saturated sodium carbonate solution is added to the solution, stirred for 30 min, and filtered at a temperature of 50-70°C during cooling of the solution, and the filter residue is collected, which is a high-purity lithium carbonate product. The purity of lithium carbonate is 99.1%, and the lithium element yield is 88.7%. Example 4

[0026] A method for preparing lithium salt from superfine particle size lepidolite, the steps comprising: Step one, the particle size of 400 purposes of superfine lithium mica is added to the mixed solution containing sodium carbonate and sodium chloride with liquid-solid mass ratio of 2.5:1, wherein the concentration of sodium carbonate in the mixed solution is 4 mol / L, and the concentration of sodium chloride is 1.2 mol / L; under the pressure of 4.5 Mpa and the temperature of 180℃, the stirring pressure is boiled for 2.5 h, the solid-liquid separation is completed before cooling to 70℃, the filter residue is collected, and the defluorination rate of the filter residue is 95.63%; Step two, after the filter residue collected in step one is dried, calcium sulfate and sodium sulfate are added, the mass ratio of sodium sulfate: calcium sulfate: filter residue is 3.5:4.5:10, the mixture is uniformly mixed and then calcined, the calcination temperature is 1100℃, the calcination time is 1 h, and the calcined material is collected; Step three, the calcined material collected in step two is added with water for leaching with liquid-solid mass ratio of 8:1, the leaching time is 2.8 h, and after sufficient reaction, the solid-liquid mixture is obtained, the residue is removed by filtration, and the filtrate is obtained as a lithium-containing leaching solution; Step four, under the room temperature condition, saturated sodium carbonate solution is added to the lithium-containing leaching solution collected in step three until no precipitate is generated, filtration is performed, and the filtrate is collected; Step five, the filtrate collected in step four is concentrated to a lithium ion concentration of 33 g / L, the solution is heated to 95℃, saturated sodium carbonate solution is added to the solution, stirring reaction is performed for 25 min, filtration is performed at a temperature in the range from 50-70℃ during the cooling of the solution, and the filter residue is collected, which is a high-purity lithium carbonate product. The purity of the lithium carbonate is 99.3%, and the lithium element yield is 87.3%. Example 5

[0027] A method for preparing lithium salt from superfine lithium mica, the steps comprising: Step one, the particle size of 500 purposes of superfine lithium mica is added to the mixed solution containing sodium carbonate and sodium chloride with liquid-solid mass ratio of 3:1, wherein the concentration of sodium carbonate in the mixed solution is 5 mol / L, and the concentration of sodium chloride is 1.5 mol / L; under the pressure of 5 Mpa and the temperature of 200℃, the stirring pressure is boiled for 3 h, the solid-liquid separation is completed before cooling to 70℃, the filter residue is collected, and the defluorination rate of the filter residue is 94.47%; Step two, after the filter residue collected in step one is dried, calcium sulfate and sodium sulfate are added, the mass ratio of sodium sulfate: calcium sulfate: filter residue is 4:5:10, the mixture is uniformly mixed and then calcined, the calcination temperature is 1100℃, the calcination time is 0.5 h, and the calcined material is collected; Step three, the calcined material collected in step two is added with water for leaching with liquid-solid mass ratio of 8:1, the leaching time is 3 h, and after sufficient reaction, the solid-liquid mixture is obtained, the residue is removed by filtration, and the filtrate is obtained as a lithium-containing leaching solution; Step four, under the room temperature condition, saturated sodium carbonate solution is added to the lithium-containing leaching solution collected in step three until no precipitate is generated, filtration is performed, and the filtrate is collected; Step five, the filtrate collected in step four is concentrated to a lithium ion concentration of 35 g / L, the solution is heated to 85 DEG C, saturated sodium carbonate solution is added to the solution, the solution is stirred for 35 min, the solution is filtered at a temperature in the range of 50-70 DEG C during cooling, the filter residue is collected, which is a high-purity lithium carbonate product. The purity of the lithium carbonate is 99.6%, and the lithium element yield is 88.2%.

[0028] The lithium carbonate prepared in embodiments 1 to 5 of the present application has high purity, the purity is all above 99.0%, and the yield is all above 87%. It can be seen that the method for preparing lithium salt from superfine particle size lepidolite can improve the selectivity of the reaction, effectively improve the purity of the prepared lithium carbonate product, effectively improve the lithium extraction efficiency of lepidolite, and reduce the loss of lithium element.

[0029] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing lithium salts from ultrafine-grained lepidolite, characterized in that, Includes the following steps: Step 1: Add ultrafine lepidolite to a mixed solution containing sodium carbonate and sodium chloride, stir and press, and complete solid-liquid separation before cooling to 70°C, then collect the filter residue. Step 2: After drying the filter residue collected in Step 1, add calcium sulfate and sodium sulfate, mix evenly, and then calcine and collect the calcined material. Step 3: Add an appropriate amount of water to the roasted material collected in Step 2 for leaching. Filter the resulting solid-liquid mixture to remove slag and obtain a lithium-containing leaching solution. Step 4: Add saturated sodium carbonate solution to the lithium-containing extract collected in Step 3 until no precipitate forms, filter, and collect the filtrate; Step 5: Concentrate the filtrate collected in Step 4, then heat it and add a saturated sodium carbonate solution. Stir the reaction and filter while hot to obtain the lithium carbonate product.

2. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, The particle size of the ultrafine lithium mica mentioned in step one is 200-600 mesh.

3. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, In step one, the liquid-solid mass ratio of the mixed solution to the ultrafine lepidolite is (1.5-3):1; the concentration of sodium carbonate in the mixed solution is 1-5 mol / L, and the concentration of sodium chloride is 0.5-1.5 mol / L.

4. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, The stirring and pressure cooking conditions in step one are: pressure 3-5 MPa, temperature 110-200℃, and time 1.5-3 hours.

5. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, In step two, the mass ratio of sodium sulfate: calcium sulfate: filter residue is (2-4):(3-5):

10.

6. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, In step two, the roasting temperature is 800-1100℃ and the roasting time is 0.5-4h.

7. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, In step three, the liquid-solid mass ratio of water to the calcined material is (2-8):1, and the immersion time is 2-3 hours.

8. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, The filtrate collected in step five is concentrated to a lithium ion concentration of 25-35 g / L.

9. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, After concentration in step five, the solution is heated to 85-95℃ and stirred for 20-40 minutes.

10. The method for preparing lithium salts from ultrafine-grained lepidolite according to claim 1, characterized in that, In step five, hot filtration means that the temperature of the solution is 50-70℃ during filtration.

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