A green and environmentally friendly method for extracting lithium

Abstract

The present invention relates to a green and environmentally friendly lithium extraction method, and the specific steps are as follows: Mix spodumene minerals with metal oxides and ball-mill them to obtain a LiAlSi₂O₆ sample with fragmented crystal lattice. Subsequently, use dilute nitric acid or dilute sulfuric acid as the leaching solution to leach out the lithium element in the LiAlSi₂O₆ sample with fragmented crystal lattice. Through simple mechanical co-grinding of α / β-LiAlSi₂O₆ with metal oxides Al₂O₃ or Fe₂O₃, the crystal structure of α / β-LiAlSi₂O₆ is destroyed and approaches amorphous, prompting the lithium element to be discrete from the crystal structure. Subsequently, a lithium extraction rate close to 100% can be achieved through mild lithium leaching conditions. This method has the advantages of simple operation, green environmental protection, energy consumption saving, etc., avoiding the disadvantages of equipment corrosion and high energy consumption brought about by extreme leaching conditions such as high temperature and strong acid in the process, and providing a new idea for extracting lithium resources from lithium ore.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing lithium compounds from ores, and particularly relates to a green and environment-friendly lithium extraction method. Background Art

[0002] With the large emission of greenhouse gases such as carbon dioxide, global warming has become a key issue faced by human development. It is necessary to promote energy conservation and emission reduction in all industries. As one of the key industries for promoting energy conservation and emission reduction, it is essential to reform and innovate traditional metallurgical processes. Traditional metallurgical processes need to be carried out under high-temperature conditions, which will consume a large amount of fossil fuels and directly emit carbon dioxide gas into the air. Therefore, new processes need to be adopted to avoid high-temperature metallurgical steps and reduce energy consumption.

[0003] Lithium, as a non-renewable mineral resource, is an indispensable raw material for the development of modern industry. Especially in recent years, the demand for lithium batteries in the new energy industry has increased sharply, and the extraction and utilization of Li resources have also become the focus of attention in the current scientific and industrial fields. Li is mainly extracted from spodumene, lepidolite, and salt lakes. At present, the grade of lithium in lepidolite is generally low, the production cost is high, and a large amount of waste residue will be generated after metallurgical lithium extraction, causing environmental damage. The method of extracting lithium from salt lake brine is limited by the high magnesium-lithium ratio in salt lake brine. Due to the similar ionic radii of magnesium and lithium ions, it is difficult to separate them, which restricts the development of lithium extraction from salt lakes in China. Therefore, spodumene ore has become the main source of lithium extraction in China. Spodumene is mainly divided into two types: α-LiAlSi2O6 and β-LiAlSi2O6. Among them, the structure of α-LiAlSi2O6 is dense and chemically inert, and it needs to undergo a phase transformation at a high temperature of 1100°C to obtain the porous β-LiAlSi2O6, and then carry out the subsequent lithium extraction process. At present, the lithium extraction process still mainly uses high-temperature combined with strong acids, supplemented by lithium carbonation for product collection. For the extraction of LiAlSi2O6 with a high lithium content, as described in the patent publication number CN102701239, the specific steps are as follows: first, α-LiAlSi2O6 is roasted at a high temperature, and the stable α-LiAlSi2O6 is transformed into β-LiAlSi2O6, then supplemented by high-temperature combined with concentrated H2SO4 leaching, and finally neutralized with alkaline substances such as calcium oxide, and filtered to obtain lithium sulfate brine. The entire lithium extraction process is cumbersome and complex. The two high-temperature roastings and the use of a large amount of acids and alkalis will cause serious corrosion to the equipment, and there are also great safety and environmental hazards.

[0004] Based on the above background, the present invention proposes a method that uses metal oxides (Al2O3 or Fe2O3) as grinding aids to break the crystal structure of LiAlSi2O6 through mechanical co-grinding, and finally leach lithium under mild low-temperature conditions. This method overcomes the drawbacks of acid consumption and energy consumption in traditional lithium extraction processes, has low energy consumption and is environmentally friendly, providing a new metallurgical process for industrial lithium extraction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a green and environmentally friendly lithium extraction method in view of the above deficiencies in the prior art. This method has a simple process, low cost, low energy consumption, does not require high temperature and strong acid leaching, and does not produce harmful waste.

[0006] To solve the above technical problem, the technical solution provided by the present invention is as follows:

[0007] Provide a green and environmentally friendly lithium extraction method, and the specific steps are as follows: Mix spodumene minerals with metal oxides and ball mill them to obtain a LiAlSi2O6 sample with fragmented crystal lattice, and then leach the lithium element in the LiAlSi2O6 sample with fragmented crystal lattice using dilute nitric acid or dilute sulfuric acid as the leaching solution.

[0008] According to the above solution, the spodumene mineral is spodumene concentrate, the main components are α-LiAlSi2O6 or β-LiAlSi2O6, and the particle size is in the micron range.

[0009] According to the above solution, the metal oxide is Al2O3 or Fe2O3.

[0010] According to the above solution, the molar ratio of the spodumene mineral to the metal oxide is 0.5 - 1.5:1. When the main component of the spodumene mineral is α-LiAlSi2O6, the molar ratio of α-LiAlSi2O6 to the metal oxide is 1.5:1; when the main component of the spodumene mineral is β-LiAlSi2O6, the molar ratio of β-LiAlSi2O6 to the metal oxide is 1:1.5.

[0011] According to the above solution, the ball milling process conditions are: ball mill at a rotation speed of 400 - 600 r / min for 1 - 10 h.

[0012] According to the above solution, the concentration of the dilute nitric acid or dilute sulfuric acid is 10 - 30 wt%.

[0013] According to the above solution, the method for leaching the lithium element in the LiAlSi2O6 sample with fragmented crystal lattice using dilute nitric acid or dilute sulfuric acid as the leaching solution is: Place the LiAlSi2O6 sample with fragmented crystal lattice in the leaching solution, and carry out heating and stirring under sealed conditions to obtain a solution containing lithium ions.

[0014] According to the above scheme, the mass-volume ratio of the lattice-fragmented LiAlSi2O6 sample to the leaching solution is 1 - 3.5 g / L.

[0015] According to the above scheme, the heating and stirring temperature is 60 - 80 °C, and the heating and stirring time is 1 - 4 h.

[0016] In the present invention, spodumene minerals are mixed and ball-milled with metal oxides. Under the continuous extrusion, shearing, crushing, and abrasion of the ball-milling medium zirconium balls, the crystal structures of α-type or β-type LiAlSi2O6 in the spodumene minerals and the grinding aids Al2O3 or Fe2O3 are damaged, and the phase gradually becomes amorphous. The lithium in the structure is also more easily stripped from the crystal structure, facilitating the subsequent mild extraction of lithium. During the ball-milling process, on the one hand, Al2O3 or Fe2O3 acts as a grinding aid to destroy the crystal structure of spodumene, and on the other hand, a chemical reaction occurs between spodumene and Al2O3 or Fe2O3, and lithium enters the structure of the metal oxide for subsequent leaching.

[0017] The beneficial effects of the present invention are as follows: The present invention provides a green and environment-friendly lithium extraction method. By simply mechanically co-milling α / β-LiAlSi2O6 with metal oxides (Al2O3 / Fe2O3), the crystal structure of α / β-LiAlSi2O6 is damaged and approaches amorphous, promoting the dispersion of lithium elements from the crystal structure. Subsequently, a very high lithium extraction rate (close to 100%) can be achieved under mild lithium leaching conditions. This method has the advantages of simple operation, green environmental protection, and energy conservation, avoiding the drawbacks of equipment corrosion and high energy consumption brought about by extreme leaching conditions such as high temperature and strong acid in the process, and providing a new idea for extracting lithium resources from lithium ores. Description of the Drawings

[0018] Figure 1 XRD patterns of the spodumene powder used in Example 1 of the present invention and the samples obtained after co-ball-milling the spodumene powder with Fe2O3 or Al2O3 respectively;

[0019] Figure 2 Comparison chart of Li leaching rates in the case of single ball-milling of spodumene powder in Example 1 and co-ball-milling of spodumene powder with grinding aids SiO2, Fe2O3, or Al2O3 respectively

[0020] Figure 3 XRD patterns of the spodumene powder used in Example 2 and the spodumene powder after co-ball-milling with Fe2O3 or Al2O3;

[0021] Figure 4 Comparison chart of Li leaching rates in the case of co-ball-milling of spodumene powder with grinding aids Fe2O3 or Al2O3 respectively in Example 2. Detailed Embodiments

[0022] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0023] In the following examples, the spodumene used is a pure mineral ore provided by a lithium ore factory in Jiangxi. The content of its useful components (α-LiAlSi2O6 or β-LiAlSi2O6) is above 90%, the main impurity is quartz, and the particle size is 5-10 microns. The grinding aid is of analytical purity and the particle size is micron-sized.

[0024] Example 1

[0025] A green and environment-friendly lithium extraction method comprises the following specific steps:

[0026] 1) Ball-mill the spodumene powder (the main component is β-LiAlSi2O6) and the grinding aid (SiO2 or Fe2O3 or Al2O3), wherein the molar ratio of β-LiAlSi2O6 to the grinding aid is 1:1.5, and the total mass of the spodumene powder and the grinding aid is 4 g. Taking the case without adding the grinding aid as a blank control sample, put the solid powder raw material into a zirconia grinding jar equipped with 7 zirconia balls with a diameter of 15 mm and a total volume of 45 mL. The ball-to-material ratio is 35:

[0027] 2, the mill speed is set at 600 rpm, the grinding duration is 2 h. After grinding, collect the solid powder to obtain 4 spodumene samples with the crystal structure destroyed.

[0028] 2) Weigh 0.35 g of the ball-milled sample obtained in step 1) and add it to 100 mL of a dilute nitric acid solution with a concentration of 10 wt% for acid leaching treatment. Place it in a stoppered container for uniform shaking reaction, then seal it with a lid and react at a water bath temperature of 80 °C for 4 h. After the reaction, let it stand for 10 min, take the supernatant and measure the Li element concentration in the solution using a flame atomic absorption spectrophotometer, and calculate the leaching rate of lithium according to the Li element concentration.

[0029] The XRD patterns of the spodumene powder used in this example and the samples obtained after co-ball milling the spodumene powder with Fe2O3 or Al2O3 are as Figure 1 shown. It can be seen that after co-ball milling the spodumene powder with Fe2O3 or Al2O3, some diffraction peaks disappear, indicating that the crystal structure of LiAlSi2O6 is destroyed and reaches a state close to amorphous, proving that when using Fe2O3 or Al2O3 as the grinding aid, there is a violent collision among the metal oxide, β-LiAlSi2O6 and the zirconia balls, and a reaction occurs between the metal oxide and β-LiAlSi2O6, and finally it exists in the form of Li2O-Si-Al / Fe, which is convenient for dissociation and recovery under the action of dilute acid in the follow-up.

[0030] Figure 2This is a comparison chart of the leaching rate of Li under the conditions of separately ball-milling spodumene powder and co-ball-milling spodumene powder with grinding aids SiO2, Fe2O3, or Al2O3. It can be seen that the leaching rate of Li is relatively low when spodumene powder is separately ball-milled or co-ball-milled with SiO2, while co-ball-milling spodumene powder with grinding aids Fe2O3 or Al2O3 can significantly improve the leaching rate of Li, and it is even close to 100% when co-ball-milled with Al2O3. The possible reason is that SiO2 has high stability and no chemical reaction occurs between it and spodumene during the ball-milling process, while a chemical reaction occurs during the co-ball-milling process of spodumene powder with Fe2O3 or Al2O3, and Li enters the structure of metal oxides, facilitating subsequent leaching.

[0031] Example 2

[0032] A green and environment-friendly lithium extraction method, the specific steps are as follows:

[0033] 1) Ball-mill spodumene powder (mainly composed of α-LiAlSi2O6) with a grinding aid (Fe2O3 or Al2O3), where the molar ratio of α-LiAlSi2O6 to the grinding aid is 1.5:1, and the total mass of spodumene powder and the grinding aid is 2 g. Put the solid powder raw material into a zirconia grinding jar equipped with 7 zirconia balls with a diameter of 15 mm and a total volume of 45 mL. The ball-to-material ratio is 35:1, the mill speed is set at 600 rpm, and the grinding duration is 2 h. After grinding, collect the solid powder to obtain 2 kinds of spodumene samples with damaged crystal structures;

[0034] 2) Weigh 0.1 g of the ball-milled sample obtained in step 1) and add it to 100 mL of a dilute nitric acid solution with a concentration of 10 wt% or a sulfuric acid solution with a concentration of 30 wt% for acid leaching treatment. Place it in a stoppered container for uniform shaking reaction, then seal it with a lid and heat it in a water bath for 4 h (the water bath temperature is 60 °C when the leaching solution is a dilute nitric acid solution, and the water bath temperature is 80 °C when the leaching solution is a sulfuric acid solution). After the reaction, let it stand for 10 min, take the supernatant and use a flame atomic absorption spectrophotometer to measure the concentration of Li element in the solution, and calculate the leaching rate of Li according to the concentration of Li element.

[0035] The XRD patterns of the spodumene powder used in this example and the spodumene powder co-ball-milled with Fe2O3 or Al2O3 are as Figure 3 shown. It can be seen that a chemical reaction occurs after ball-milling Fe2O3 or Al2O3 with α-LiAlSi2O6, and the product after ball-milling exists in the form of a complex state of Li2O-Si-Al / Fe, facilitating subsequent acid leaching.

[0036] Figure 4This is a comparison chart of the leaching rates of Li when spodumene powder is co-ball milled with the grinding aids Fe2O3 or Al2O3 in this embodiment. It can be seen that when a 10wt% dilute nitric acid solution is used as the leaching solution, the lithium leaching rate is about 62%, while when a 30wt% sulfuric acid solution is used as the leaching solution, the lithium leaching rate reaches 70-75%.

Claims

1. A green and environmentally friendly lithium extraction method, characterized in that, The specific steps are as follows: Mix spodumene minerals with metal oxides and ball-mill them to obtain a LiAlSi₂O₆ sample with fragmented lattice. Subsequently, leach the lithium element in the fragmented LiAlSi₂O₆ sample with dilute nitric acid or dilute sulfuric acid as the leaching solution, and the metal oxide is Al₂O₃ or Fe₂O₃.

2. The green and environment-friendly lithium extraction method according to claim 1, wherein The spodumene mineral is spodumene concentrate, with the main component being α-LiAlSi₂O₆ or β-LiAlSi₂O₆, and the particle size is in the micron range.

3. The green and environment-friendly lithium extraction method according to claim 1, characterized in that, The molar ratio of the spodumene mineral to the metal oxide is 0.5 - 1.5:

1.

4. The green and environmentally friendly lithium extraction method according to claim 1, characterized in that The ball-milling process conditions are: ball-mill for 1 - 10 h at a rotation speed of 400 - 600 r / min.

5. The green and environment-friendly lithium extraction method according to claim 1, characterized in that The concentration of the dilute nitric acid or dilute sulfuric acid is 10 - 30 wt%.

6. The green and environment-friendly lithium extraction method according to claim 1, wherein The method for leaching the lithium element in the fragmented LiAlSi₂O₆ sample with dilute nitric acid or dilute sulfuric acid as the leaching solution is: Place the fragmented LiAlSi₂O₆ sample in the leaching solution, and carry out heating and stirring under sealed conditions to obtain a solution containing lithium ions.

7. The green and environment-friendly lithium extraction method according to claim 1, characterized in that, The mass-volume ratio of the fragmented LiAlSi₂O₆ sample to the leaching solution is 1 - 3.5 g / L.

8. The green and environment-friendly lithium extraction method according to claim 6, characterized in that, The heating and stirring temperature is 60 - 80 °C, and the heating and stirring time is 1 - 4 h.

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