Method for preparing high-purity lithium nitrate by pyrolyzing and separating aluminum and lithium in lepidolite leaching solution

Abstract

The invention provides a method for preparing high-purity lithium nitrate by pyrolyzing and separating aluminum and lithium in a lepidolite leaching solution, and relates to the technical field of lithium nitrate preparation, which comprises the following steps: ball-milling lepidolite; adding water into the ball-milled lepidolite, pulping, adding nitric acid, carrying out nitric acid pressure leaching reaction, and filtering a solid-liquid mixture obtained by the reaction to obtain leachate and leaching residues; carrying out negative pressure evaporation concentration on the leachate to obtain a mixed solid of lithium nitrate and aluminum nitrate, and calcining and pyrolyzing to obtain a solid mixture of aluminum oxide and lithium nitrate and nitric oxide gas; dissolving the solid mixture in water, and separating to obtain crude aluminum oxide and a lithium nitrate solution; and sequentially carrying out negative pressure evaporation concentration, resin impurity removal and evaporation crystallization on the obtained lithium nitrate solution to obtain high-purity lithium nitrate and crystallization mother liquor. The materials used in the invention are common industrial products, are easy to purchase and are low in price; the whole technological process is simple, easy to operate, environment-friendly and easy to implement on a production line.

Description

Technical Field

[0001] This invention relates to the field of lithium nitrate preparation technology, and in particular to a method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution. Background Technology

[0002] Lithium is mainly used in batteries, ceramics, glass, and pharmaceuticals, with batteries accounting for 56% of its applications. In recent years, the new energy industry has driven the rapid development of the lithium battery industry, and the global demand for lithium resources has been rising continuously. Lithium is a strategic resource in the new energy era.

[0003] Currently, the mainstream process for lithium extraction from spodumene is the sulfuric acid process, with lithium carbonate as its main product. However, some companies require lithium nitrate, which can directly react with manganese nitrate, nickel nitrate, and cobalt to synthesize ternary cathode materials, eliminating the need for the cumbersome process of first preparing nickel, cobalt, and manganese as ternary precursors before reacting them with lithium to synthesize the ternary cathode material. Research on the extraction of lithium from spodumene to prepare lithium nitrate is relatively limited. With changing market demands and increasing national environmental awareness, the efficient, economical, environmentally friendly, and comprehensive utilization of metallic lithium from spodumene resources to prepare lithium nitrate is of great significance.

[0004] Chinese patent CN102602967A discloses a method for preparing lithium nitrate, which includes adding lithium hydroxide to lithium sulfate to adjust the pH to 11-12, using calcium nitrate to remove sulfate ions, and evaporating, concentrating, and crystallizing the resulting filtrate to obtain lithium nitrate. This method produces a large amount of calcium slag during sulfate removal.

[0005] Chinese patent CN118183806A discloses a method for preparing lithium nitrate and lithium nitrate, including pretreatment of a low-lithium solution with alkali, extraction of lithium by extraction, and back-extraction of nitrate to obtain a lithium nitrate solution. This method introduces organic matter through extraction, and improper handling can result in lithium nitrate containing organic matter, affecting its use. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution. This method uses spodumene as raw material, and through pressurized nitric acid leaching, lithium can be fully extracted from the spodumene. The resulting leaching solution is then calcined and pyrolyzed to obtain NO. x A solid mixture of gas, lithium nitrate, and aluminum oxide; NO x After gas treatment, a nitric acid solution is obtained, which can be reused for pressurized nitric acid leaching. The solid mixture is separated by water dissolution to obtain crude alumina and lithium nitrate solution. The lithium nitrate solution is concentrated by negative pressure evaporation to obtain a high-concentration lithium nitrate solution. After impurity removal, a high-purity lithium nitrate solution is obtained. The high-purity lithium nitrate solution is then concentrated by negative pressure evaporation and crystallization to obtain high-purity lithium nitrate.

[0007] Compared with existing technologies, this invention provides a novel method for preparing lithium nitrate, comprising using calcination to decompose and separate lithium and aluminum from spodumene leaching solution, and then producing lithium nitrate and alumina respectively. Unlike traditional methods that use lithium sulfate, lithium carbonate, or lithium hydroxide to prepare lithium nitrate, this invention directly obtains a mixed solution of lithium nitrate from the mineral leaching end, and after simple impurity removal and separation, obtains high-purity lithium nitrate. The process is simple and efficient.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] One objective of this invention is to provide a method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution, comprising the following steps:

[0010] S1. Ball mill the spodumene.

[0011] S2. Add water to the spodumene ore ball-milled in step S1 to make a slurry, then add nitric acid to the slurry to carry out a nitric acid pressure leaching reaction, and filter the solid-liquid mixture obtained from the reaction to obtain leaching solution and leaching residue.

[0012] S3. The leachate obtained in step S2 is first concentrated by negative pressure evaporation to obtain a mixed solid of lithium nitrate and aluminum nitrate. Then, the mixed solid is calcined and pyrolyzed to obtain a solid mixture of aluminum oxide and lithium nitrate and nitrogen oxide gas. The nitrogen oxide gas is used to prepare nitric acid. The obtained nitric acid can be returned to the pressurized nitric acid leaching reaction in step S2.

[0013] S4. The solid mixture obtained in step S3 is dissolved in water and then separated to obtain crude alumina and lithium nitrate solution.

[0014] S5. The lithium nitrate solution obtained in step S4 is subjected to negative pressure evaporation and concentration, resin impurity removal and evaporation crystallization in sequence to obtain high-purity lithium nitrate and crystallization mother liquor. The crystallization mother liquor is used for repeated evaporation and crystallization.

[0015] Preferably, in step S1, the average particle size of the ball-milled spodumene is less than 48 μm.

[0016] Preferably, in step S2, spodumene and water are pulped at a liquid-to-solid mass ratio of (2~5):1. In the pressurized nitric acid leaching reaction, the amount of nitric acid used is calculated as 100~160wt% of the theoretical amount required for the main elements Li, Na, K, Al, Fe, Mn, Ca, and Mg participating in the leaching reaction. The temperature of the pressurized nitric acid leaching reaction is 120~180℃, the pressure is 0.35~0.65MPa, and the reaction time is 2~5h.

[0017] Preferably, in step S3, the negative pressure evaporation and concentration temperature is 90~100℃, and the evaporation and concentration pressure is -0.01~-0.1MPa. Based on the characteristic that aluminum nitrate begins to decompose at 200℃ and lithium nitrate begins to decompose at 600℃, the calcination pyrolysis temperature is set at 200~500℃. This way, after calcination pyrolysis, aluminum nitrate is converted into aluminum oxide, while the lithium nitrate phase remains unchanged, thus allowing for the separation of aluminum and lithium through a subsequent leaching process.

[0018] Preferably, in step S4, the solid mixture is dissolved in water at a liquid-solid mass ratio of (2~5):1, and the dissolution temperature is 20~40℃.

[0019] Preferably, in step S4, the temperature for negative pressure evaporation concentration and evaporation crystallization is 90~100℃.

[0020] In some preferred embodiments, the spodumene leaching solution obtained in step S2 comprises the following components: Li 2-3 g / L, Al 4-5 g / L, Fe 0.3-0.9 g / L, Na 0.1-0.5 g / L, Ca 0.2-0.5 g / L, K 0.1-0.5 g / L, Mg 0.02-0.09 g / L, and Si 0.02-0.09 g / L. The method of the present invention is more suitable for the efficient extraction of lithium and aluminum from spodumene with this preferred composition.

[0021] The technical solution provided by this invention has at least the following beneficial effects:

[0022] This invention provides a novel method for preparing lithium nitrate, comprising pressurized leaching of spodumene with nitric acid, followed by evaporation and concentration of the leachate to obtain a mixed solid of lithium nitrate and aluminum nitrate. The resulting solid is then calcined, pyrolyzed, and water-soluble to yield a lithium nitrate solution and crude alumina. The lithium nitrate solution can be used to prepare high-purity lithium nitrate. Furthermore, the nitric acid used in the process can be recycled, maximizing the utilization of spodumene resources and improving economic efficiency. The materials used in this invention are all common industrial products, readily available and inexpensive; the entire process is simple, easy to operate, environmentally friendly, and easily implemented on a production line. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a process flow diagram of the present invention for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution. Detailed Implementation

[0025] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0026] This invention provides a method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution. The method includes the following steps: ball milling spodumene; adding water to the ball-milled spodumene to form a slurry, then adding nitric acid to the slurry for pressurized nitric acid leaching; filtering the resulting solid-liquid mixture to obtain leaching solution and leaching residue; evaporating and concentrating the obtained leaching solution to obtain a mixed solid of lithium nitrate and aluminum nitrate, which is then calcined and pyrolyzed to obtain NO. x A solid mixture of gas, lithium nitrate, and aluminum oxide; NO x After gas treatment, a nitric acid solution is obtained, which can be reused for pressurized nitric acid leaching. The solid mixture is separated by aqueous dissolution to obtain crude alumina and a lithium nitrate solution. The lithium nitrate solution is then concentrated by negative pressure evaporation to obtain a high-concentration lithium nitrate solution. This high-purity lithium nitrate solution is then purified by impurity removal, followed by negative pressure evaporation, concentration, and crystallization to obtain high-purity lithium nitrate. This invention uses a simple method to prepare lithium nitrate. The nitric acid generated in the process can be recycled back into the process, enabling efficient resource utilization and maximizing benefits with minimal resource consumption and environmental costs.

[0027] The analysis results of each component of the lithium spodumene leaching solution used in the key process of pyrolysis separation in all the following examples and comparative examples are shown in Table 1, and the technical control requirements of the obtained pure lithium nitrate solution are shown in Table 2.

[0028] Table 1. Component analysis results of spodumene leaching solution

[0029]

[0030] Table 2 Technical Specifications Control Requirements for Pure Lithium Nitrate Solution

[0031]

[0032] Example 1

[0033] A process flow diagram of the present invention for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution is shown below. Figure 1 As shown, the detailed steps are as follows:

[0034] Step 1: Ball mill the spodumene. After ball milling, the average particle size of the spodumene is less than 48 μm.

[0035] Step 2: The pretreated spodumene ore from Step 1 is mixed with water at a liquid-to-solid mass ratio of 3:1 and the slurry is subjected to pressurized nitric acid leaching. The amount of nitric acid used is 100wt% of the theoretical amount required based on the main elements participating in the leaching reaction, namely Li, Na, K, Al, Fe, Ca, and Mg. The leaching reaction temperature is 160℃, the pressure is 0.5MPa, and the leaching reaction time is 3h. The resulting solid-liquid mixture is filtered to obtain leachate and leaching residue.

[0036] Step 3: The leachate obtained in Step 2 is evaporated and concentrated at a negative pressure of 0.05 MPa and 95°C to obtain a mixed solid of aluminum nitrate and lithium nitrate. Then, it is calcined and pyrolyzed at 250°C±15°C to obtain a solid mixture of aluminum oxide and lithium nitrate and nitrogen oxide gas. The nitrogen oxide gas is used to prepare nitric acid, and the nitric acid is returned to the pressurized leaching reaction of nitric acid in Step 1.

[0037] Step 4: Dissolve the solid mixture of alumina and lithium nitrate obtained in Step 3 in water at a liquid-solid mass ratio of 3:1, stir and react for 30 minutes, then filter to separate and obtain a crude alumina and lithium nitrate solution.

[0038] Step 5: The lithium nitrate solution obtained in Step 4 is concentrated by negative pressure evaporation at 95°C to obtain a high-concentration lithium nitrate solution; the high-concentration lithium nitrate solution is then purified by resin to obtain a pure lithium nitrate solution (composition shown in Table 3); finally, the pure lithium nitrate solution is evaporated and cooled to crystallize at 95°C to obtain high-purity lithium nitrate and crystallization mother liquor, which is used for repeated evaporation and crystallization.

[0039] After washing the solid mixture in step 4, the crude alumina contains 0.0095% lithium and the lithium nitrate solution contains 0.0007 g / L aluminum.

[0040] The experiment achieved a 90% recovery rate for lithium and an 85.48% recovery rate for aluminum throughout the entire process.

[0041] Table 3 Composition of pure lithium nitrate solution

[0042]

[0043] Example 2

[0044] A method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution is implemented according to the method described in Example 1, with the following difference:

[0045] In step 3, the calcination pyrolysis temperature is 500℃±15℃.

[0046] After washing the solid mixture in step 4, the crude alumina contains 0.023% lithium and the lithium nitrate solution contains 0.004 g / L aluminum.

[0047] The composition of the pure lithium nitrate solution obtained in this experiment is shown in Table 4. The total recovery rate of lithium nitrate was 89%, and the total recovery rate of aluminum was 83%.

[0048] Table 4 Composition of pure lithium nitrate solution

[0049]

[0050] Example 3

[0051] A method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution is implemented according to the method described in Example 1, with the following difference:

[0052] In step 2, the spodumene ore pretreated in step 1 is mixed with water at a liquid-solid mass ratio of 4:1, and the slurry is subjected to pressurized nitric acid leaching. The amount of nitric acid used is 110% of the theoretical amount, the leaching reaction temperature is 170℃, and the leaching reaction time is 3h.

[0053] In step 3, the calcination pyrolysis temperature is 300℃±15℃.

[0054] The composition of the pure lithium nitrate solution obtained in this experiment is shown in Table 5. The total lithium recovery rate was 87.5%, and the total aluminum recovery rate was 91.0%.

[0055] Table 5 Composition of pure lithium nitrate solution

[0056]

[0057] Comparative Example 1

[0058] A method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution is implemented according to the method described in Example 1, with the following difference:

[0059] In step 3, the calcination pyrolysis temperature is 700℃±15℃.

[0060] After washing the solid mixture in step 4, the crude alumina contains 4.1% lithium and the lithium nitrate solution contains 0.0004 g / L aluminum.

[0061] The composition of the pure lithium nitrate solution obtained in this experiment is shown in Table 6. The total lithium yield was 40%, which is much lower than that in Example 1.

[0062] Table 6 Composition of Pure Lithium Nitrate Solution

[0063]

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution, characterized in that, Includes the following steps: S1. Ball mill the spodumene. S2. Add water to the spodumene ore ball-milled in step S1 to make a slurry, then add nitric acid to the slurry to carry out a nitric acid pressure leaching reaction, and filter the solid-liquid mixture obtained from the reaction to obtain leaching solution and leaching residue. S3. The leachate obtained in step S2 is first concentrated by negative pressure evaporation to obtain a mixed solid of lithium nitrate and aluminum nitrate. Then, the mixed solid is calcined and pyrolyzed to obtain a solid mixture of aluminum oxide and lithium nitrate and nitrogen oxide gas. S4. The solid mixture obtained in step S3 is dissolved in water and then separated to obtain crude alumina and lithium nitrate solution. S5. The lithium nitrate solution obtained in step S4 is subjected to negative pressure evaporation and concentration, resin impurity removal and evaporation crystallization in sequence to obtain high-purity lithium nitrate and crystallization mother liquor. The crystallization mother liquor is used for repeated evaporation and crystallization.

2. The method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, characterized in that, In step S1, the average particle size of the ball-milled spodumene is less than 48 μm.

3. The method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, characterized in that, In step S2, spodumene and water are pulped at a liquid-solid mass ratio of (2~5):

1. In the pressurized nitric acid leaching reaction, the amount of nitric acid used is calculated as 100~160wt% of the theoretical amount required for the main elements Li, Na, K, Al, Fe, Mn, Ca and Mg participating in the leaching reaction. The temperature of the pressurized nitric acid leaching reaction is 120~180℃, the pressure is 0.35~0.65MPa, and the reaction time is 2~5h.

4. The method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, characterized in that, In step S3, the negative pressure evaporation and concentration temperature is 90~100℃, the negative pressure range is -0.01~-0.1Mpa, and the calcination and pyrolysis temperature is 200~500℃.

5. The method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, characterized in that, In step S3, nitrogen oxide gas is used to prepare nitric acid, and the resulting nitric acid can be returned to the pressurized leaching reaction of nitric acid in step S2.

6. In the method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, in step S4, the solid mixture is dissolved in water at a liquid-solid mass ratio of (2~5):1, and the dissolution temperature is 20~40℃.

7. In the method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, the temperature of negative pressure evaporation concentration and evaporation crystallization in step S4 is 90~100℃.

8. The method for preparing high-purity lithium nitrate by pyrolysis separation of aluminum and lithium from spodumene leaching solution according to claim 1, wherein the components of the spodumene leaching solution obtained in step S2 include: Li 2-3g / L, Al 4-5 g / L, Fe 0.3-0.9 g / L, Na0.1-0.5 g / L, Ca 0.2-0.5g / L, K 0.1-0.5g / L, Mg 0.02-0.09g / L, Si 0.02-0.09g / L.

Images