NaOH-NaAlO2 combined leaching lithium extraction process taking low-grade alpha-spodumene as raw material

Abstract

The invention provides a NaOH-NaAlO2 combined leaching lithium extraction process by taking low-grade alpha-spodumene as a raw material. The process is realized by the following technical scheme: crushing and grinding the low-grade alpha-spodumene to prepare powder with the particle size of less than or equal to 200 microns; mixing the powder with a NaOH-NaAlO2 mixed solution to prepare slurry, performing hydrothermal reaction on the slurry in a high-pressure reaction kettle, and replacing Na < + > and Li < + > to obtain lithium hydroxide; filtering lithium hydroxide to obtain filter residues and filtrate; drying filter residues to obtain a molecular sieve; performing concentration and impurity removal on the filtrate, performing lithium precipitation to obtain a lithium carbonate crude product, adding a small amount of sodium hydroxide into the filtrate after lithium precipitation, and circulating the filtrate as circulating mother liquor; according to the method, mineral separation and roasting are not needed, the problems that alpha-spodumene needs to be subjected to high-temperature roasting and crystal transformation into beta-spodumene and alpha-spodumene needs to be subjected to high-temperature roasting and crystal transformation into beta-spodumene can be solved, and the method has the advantages of being low in energy consumption cost, short in process, environmentally friendly, simple in process, easy to operate and high in additional value of reaction residues.

Description

Technical Field

[0001] The invention relates to the technical field of industrial lithium extraction, and in particular to a NaOH-NaAlO2 combined leaching process for lithium extraction using low-grade alpha-spodumene as a raw material. Background Art

[0002] In recent years, lithium has been increasingly used in aerospace, nuclear power generation, battery energy and other fields. It has become a very important metal in industrial production and is known as the "energy metal of the 21st century". Lithium exists in two forms in nature: one is in the form of lithium-containing ores such as spodumene, lepidolite, and petalite, and the other is in the form of lithium ions in salt lake brine, underground brine and seawater.

[0003] There are three crystal forms of spodumene: α, β and γ. Natural spodumene is α-type spodumene, which is one of the most commonly used lithium-containing mineral resources in the world. Currently, the industry generally uses high temperatures of about 1050℃ to transform it into β-type spodumene with higher activity before extracting lithium salts.

[0004] Publication No. CN110510642A discloses a method for economically extracting lithium from low-grade α spodumene, which comprises crushing and grinding the low-grade α spodumene into powder with a particle size of ≤150 μm; then uniformly mixing the obtained powder with sodium hydroxide, sodium carbonate and water to form a slurry, and extracting the lithium in the spodumene into lithium carbonate through a hydrothermal reaction; filtering after the reaction, the obtained filtrate is supplemented with the consumed sodium hydroxide and sodium carbonate and then recycled for the hydrothermal reaction, the obtained filter residue is washed and then added with water to form a slurry, which is sent to a reactor, and an excess of CO2 is introduced for reaction, so that the lithium carbonate in the slurry is converted into soluble lithium bicarbonate; after the reaction is completed, filtering and washing, the obtained filtrate is subjected to thermal decomposition to obtain a lithium carbonate product, and the filter residue is sorted and dried to obtain a high-value-added analcime; it discloses a technical solution for extracting lithium using sodium hydroxide.

[0005] However, in actual application, the above-mentioned public technology still cannot solve the problem that low-grade α-spodumene needs to be processed, resulting in Li2O loss, and α-spodumene needs to be calcined at high temperature to be converted into β-spodumene; and it has the defects of high energy consumption cost, long process, unfriendly environment and low added value of reaction slag. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a NaOH-NaAlO2 combined leaching lithium extraction process using low-grade α-spodumene as raw material, so as to more accurately solve the problems of high energy consumption cost, long process, unfriendly environment and low added value of reaction slag in the existing lithium extraction process.

[0007] The present invention is achieved by the following technical scheme: a NaOH-NaAlO2 combined leaching process for lithium extraction using low-grade α-spodumene as raw material, characterized in that it comprises the following steps: The low-grade α-spodumene is crushed and ground into powder with a particle size of ≤200μm; The obtained powder is mixed with a NaOH-NaAlO2 mixed solution to form a slurry, and the slurry is subjected to a hydrothermal reaction in a high-pressure reactor to replace Na+ and Li+ to obtain lithium hydroxide; The lithium hydroxide is filtered to obtain a filter residue and a filtrate; Drying the filter residue to obtain a molecular sieve; The filtrate is concentrated and impurities are removed, and then lithium is precipitated to obtain crude lithium carbonate. A small amount of sodium hydroxide is added to the filtrate after lithium precipitation and the filtrate is circulated as a circulating mother liquor.

[0008] Furthermore, the Li2O content in the low-grade α-spodumene is 1.67%.

[0009] Furthermore, the specific steps of crushing and grinding low-grade α-spodumene to prepare a powder with a particle size of ≤200 μm are as follows: first, the low-grade α-spodumene is placed in a crusher for preliminary coarse crushing to break it into 3-10 mm particles, and then the particles are added to a mill for continuous grinding, the ground fine-grained ore powder is screened, and the coarse particles larger than 200 μm are returned to the grinding process again to ensure that the particle size of all powders does not exceed 200 μm.

[0010] Furthermore, the liquid-to-solid ratio of the NaOH-NaAlO2 mixed solution to the powder is 10:1, and the NaOH-NaAlO2 mixed solution and the powder are stirred uniformly at 100 r / min to form a slurry.

[0011] Furthermore, the reaction temperature of the hydrothermal reaction in the high-pressure reactor is 260° C., the reaction time is 4 h, and the reaction speed is 400 r / min.

[0012] Furthermore, ultrapure water is added to the obtained filter residue, stirred evenly, and then allowed to stand, and then the supernatant is filtered, and all the filtrate and washing liquid are collected after repeated washing four or five times.

[0013] Furthermore, the filter residue is dried in a vacuum drying oven or a hot air circulation oven at a drying temperature of 120-140°C.

[0014] Furthermore, the specific steps of concentrating the filtrate and removing impurities and then precipitating lithium to obtain a crude lithium carbonate product are: using an evaporator or a concentrator to concentrate the filtrate, adding sodium hydroxide or calcium hydroxide after the filtrate is concentrated, precipitating or complexing impurities in the filtrate, and then centrifuging to separate a clean filtrate to complete impurity removal, adding an alkaline agent to the filtrate after impurity removal to combine it with lithium ions in the filtrate to form lithium carbonate, and finally the lithium carbonate is precipitated in the form of a precipitate, and the precipitated lithium carbonate is separated by a centrifuge or a filter machine, and dried to obtain a crude lithium carbonate product.

[0015] Beneficial effects of the present invention: The invention proposes a NaOH-NaAlO2 combined leaching lithium extraction process using low-grade α-spodumene as a raw material, which does not require ore dressing and roasting, and can solve the problem that α-spodumene needs high-temperature roasting to be crystallized into β-spodumene and the problem that α-spodumene needs high-temperature roasting to be crystallized into β-spodumene. The reaction slag can obtain a molecular sieve by-product with high added value, and solves the problems of long process and high sodium hydroxide consumption in traditional spodumene lithium extraction. The invention has the advantages of low energy consumption cost, short process, environmental friendliness, simple and easy process operation, and high added value of reaction slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention provides a schematic diagram of a NaOH-NaAlO2 combined leaching process for lithium extraction using low-grade α-spodumene as raw material. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] Reference Figure 1 The present invention provides a schematic diagram of a NaOH-NaAlO2 combined leaching process for lithium extraction using low-grade α-spodumene as raw material, comprising the following steps: A NaOH-NaAlO2 combined leaching process for lithium extraction using low-grade α-spodumene as raw material comprises the following steps: S1. Crushing and grinding low-grade α-spodumene into powder with a particle size of ≤200μm. The Li2O content in low-grade α-spodumene is 1.67%. Specifically, the low-grade α-spodumene is firstly put into a crusher for preliminary coarse crushing, and crushed into 3-10mm fragments. Then the fragments are added to a mill for continuous grinding. The ground fine-grained ore powder is screened, and the coarse particles larger than 200μm are returned to the grinding process again to ensure that the particle size of all powders does not exceed 200μm.

[0019] S2. The obtained powder is mixed with a NaOH-NaAlO2 mixed solution to form a slurry, the liquid-to-solid ratio of the NaOH-NaAlO2 mixed solution to the powder is 10:1, the NaOH-NaAlO2 mixed solution and the powder are stirred evenly at 100 r / min to form a slurry, the slurry is subjected to a hydrothermal reaction in a high-pressure reactor, Na+ and Li+ are replaced to obtain lithium hydroxide, the reaction temperature of the hydrothermal reaction in the high-pressure reactor is 260°C, the reaction time is 4h, and the reaction rate is 400 r / min.

[0020] S3, filtering lithium hydroxide to obtain filter residue and filtrate, adding ultrapure water to the obtained filter residue, stirring evenly, letting it stand, and then filtering the supernatant, repeatedly washing four or five times and collecting all the filtrate and washing liquid; specifically, 1. preparing a filter (such as filter paper or filter membrane) and a container for collecting the filtrate; 2. pouring the slurry containing lithium hydroxide into the filter, allowing the filtrate to pass through the filter and the filter residue to remain on the filter; 3. transferring the filtered filter residue to a container; 4. adding an appropriate amount of ultrapure water to the filter residue, and stirring evenly with a stirring rod to fully mix the filter residue with water; 5. standing for a period of time to allow the solid suspended in the water to settle; 6. pouring the mixture into the filter again, allowing the supernatant to pass through the filter and the solid precipitate to remain on the filter; 7. repeating steps 5 and 6, and washing four to five times to ensure that the impurities in the filter residue are removed as much as possible; 8. collecting the filtrate and washing liquid obtained from each filtration to ensure that all the filtrate and washing liquid are collected, and the obtained filtrate and washing liquid contain relatively pure lithium hydroxide.

[0021] S4. Dry the filter residue to obtain a molecular sieve. The filter residue is dried in a vacuum drying oven at a drying temperature of 120°C. Specifically, prepare a vacuum drying oven and preheat it to 120°C. Transfer the filter residue to a container suitable for drying. Place the container in the preheated vacuum drying oven. According to the instructions for use of the equipment, select a suitable drying mode and time. Ensure that the equipment is in a negative pressure state and perform appropriate vacuum operations. Start the drying process and monitor as needed to ensure that the temperature is controlled at 120°C. During the drying process, the degree of dryness of the filter residue can be checked regularly. If the filter residue is observed to be dry and there is no obvious sense of moisture, it can be considered that the drying is complete. Once the desired degree of dryness is reached, turn off the drying equipment and wait for the filter residue to cool to room temperature. After cooling, the dried filter residue can be transferred to a sealed container to prevent further moisture absorption.

[0022] S5. The filtrate is concentrated and impurities are removed, and then lithium is precipitated to obtain crude lithium carbonate. Specifically, the filtrate is concentrated by an evaporator or a concentrator, and the purpose is to increase the concentration of lithium in the filtrate by partially evaporating the solvent (such as water) in the filtrate. After the filtrate is concentrated, sodium hydroxide or calcium hydroxide is added to precipitate or complex the impurities (such as iron, magnesium, and sodium) in the filtrate, and then centrifugal filtration is performed to separate the clean filtrate to complete the impurity removal. Lithium precipitation usually involves combining the lithium ions in the filtrate with carbonate ions, and adding an alkaline reagent (such as sodium carbonate, sodium bicarbonate) to the filtrate after impurities are removed to combine it with the lithium ions in the filtrate to form lithium carbonate. Finally, the lithium carbonate is precipitated. The precipitated lithium carbonate is separated by a centrifuge or a filtering machine, and dried to obtain crude lithium carbonate. A small amount of sodium hydroxide is added to the filtrate after lithium precipitation and circulated as a circulating mother liquor.

[0023] The reaction equations for the related reactions are as follows:

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] The invention proposes a NaOH-NaAlO2 combined leaching lithium extraction process using low-grade α-spodumene as a raw material, which does not require ore dressing and roasting, and can solve the problem that α-spodumene needs high-temperature roasting to be crystallized into β-spodumene and the problem that α-spodumene needs high-temperature roasting to be crystallized into β-spodumene. The reaction slag can obtain a molecular sieve by-product with high added value, and solves the problems of long process and high sodium hydroxide consumption in traditional spodumene lithium extraction. The invention has the advantages of low energy consumption cost, short process, environmental friendliness, simple and easy process operation, and high added value of reaction slag.

[0030] Of course, the present invention may have many other implementations. Based on this implementation, other implementations obtained by ordinary technicians in this field without any creative work are all within the scope of protection of the present invention.

Claims

1. A NaOH-NaAlO2 combined leaching process for lithium extraction using low-grade α-spodumene as raw material, characterized in that: The following steps are involved: The low-grade α-spodumene is crushed and ground into powder with a particle size of ≤200μm; The obtained powder is mixed with a NaOH-NaAlO2 mixed solution to form a slurry, and the slurry is subjected to a hydrothermal reaction in a high-pressure reactor to replace Na+ and Li+ to obtain lithium hydroxide; The lithium hydroxide is filtered to obtain a filter residue and a filtrate; Drying the filter residue to obtain a molecular sieve; The filtrate is concentrated and impurities are removed, and then lithium is precipitated to obtain crude lithium carbonate. A small amount of sodium hydroxide is added to the filtrate after lithium precipitation and the filtrate is circulated as a circulating mother liquor.

2. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: The Li2O content in the low-grade α-spodumene is 1.67%.

3. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: The specific steps of crushing and grinding low-grade α-spodumene to prepare powder with a particle size of ≤200 μm are as follows: first, the low-grade α-spodumene is placed in a crusher for preliminary coarse crushing to crush it into 3-10 mm particles, and then the particles are added to a mill for continuous grinding, the ground fine-grained ore powder is screened, and the coarse particles larger than 200 μm are returned to the grinding process again to ensure that the particle size of all powders does not exceed 200 μm.

4. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: The liquid-to-solid ratio of the NaOH-NaAlO2 mixed solution to the powder is 10:1, and the NaOH-NaAlO2 mixed solution and the powder are stirred evenly at 100 r / min to form a slurry.

5. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction in the high-pressure reactor is 260° C., the reaction time is 4 h, and the reaction speed is 400 r / min.

6. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: Ultrapure water is added to the obtained filter residue, stirred evenly, and then allowed to stand, and then the supernatant is filtered. After repeated washing four or five times, all the filtrate and washing liquid are collected.

7. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: The filter residue is dried in a vacuum drying oven or a hot air circulation oven at a drying temperature of 120-140°C.

8. The NaOH-NaAlO2 combined leaching and lithium extraction process using low-grade α-spodumene as raw material according to claim 1, characterized in that: The specific steps of concentrating the filtrate and removing impurities and then precipitating lithium to obtain a crude lithium carbonate product are: using an evaporator or a concentrator to concentrate the filtrate, adding sodium hydroxide or calcium hydroxide after the filtrate is concentrated, precipitating or complexing impurities in the filtrate, and then centrifuging to separate a clean filtrate to complete impurity removal, adding an alkaline agent to the filtrate after impurity removal to combine it with lithium ions in the filtrate to form lithium carbonate, and finally the lithium carbonate is precipitated in the form of a precipitate, and the precipitated lithium carbonate is separated by a centrifuge or a filtering machine, and dried to obtain a crude lithium carbonate product.

Images