Method for efficiently extracting lithium by roasting lepidolite at low temperature by using composite organic acid

Abstract

The invention relates to a method for efficiently extracting lithium by roasting lepidolite at low temperature by using composite organic acid. The invention relates to a method for efficiently extracting lithium by roasting lepidolite at low temperature by using composite organic acid, which comprises the following steps of: adding an activating agent into lepidolite concentrate, and pre-activating to obtain activated lepidolite concentrate powder; the lepidolite concentrate powder and a composite organic acid roasting agent are mixed, acidified and roasted, and a roasted product is obtained; adding water into the roasted product for leaching, and carrying out suction filtration to obtain a lithium-containing leachate; the composite organic acid roasting agent at least comprises methanesulfonic acid. According to the method, the problem that the lithium ion extraction efficiency is low due to the fact that the TOT layered structure in the lepidolite is difficult to damage is solved, and the problem that the lithium ion extraction efficiency is low due to the fact that Si-O bonds with high bond energy in an existing lepidolite crystal framework are difficult to dissociate is also solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from ores, and in particular to a method for efficiently extracting lithium from lepidolite by low-temperature roasting with a composite organic acid. Background Art

[0002] Lithium, a strategic resource, plays a crucial role in numerous fields, including new energy, electronics, and aerospace. With the rapid development of industries like electric vehicles and energy storage batteries, demand for lithium continues to rise. Lepidolite, a lithium-rich mineral resource, holds enormous development potential.

[0003] Lepidolite is a monoclinic layered silicate mineral with a unique crystal structure. Its framework is a TOT-type three-layer structure composed of two interconnected layers of SiO₄ tetrahedra and AlO₆ octahedra. This structure endows lepidolite with relatively stable physical and chemical properties. However, this very stable structure also presents significant challenges for lithium ion extraction.

[0004] In the crystal structure of lepidolite, Al 3+ Isomorphic substitution of part Si will occur 4+ , which leads to an unbalanced state of charge between the layers. In order to maintain charge balance, Li + , K + Alkali metal ions such as lithium ions will be embedded in it to compensate. As a result, lithium ions are locked inside the stable silicate lattice and difficult to release freely. If lithium ions are to be extracted from lepidolite, its TOT layered structure must be destroyed, but this process faces many difficulties.

[0005] The Si-O bond is one of the key chemical bonds that make up the crystal skeleton of lepidolite, and its bond energy is high, approximately 460 kJ / mol. This means that under normal temperature and pressure conditions, the Si-O bond is almost impossible to dissociate, making it difficult to effectively extract lithium ions from lepidolite using conventional chemical or physical methods. Therefore, how to efficiently and economically extract lithium ions from lepidolite, break its stable TOT layered structure, and overcome the obstacles brought about by the high bond energy of the Si-O bond has become a technical problem that needs to be solved urgently in the current field of lithium resource development. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid, so as to solve the problem that the TOT layered structure in lepidolite is difficult to destroy, resulting in low lithium ion extraction efficiency. It can also solve the problem that the high bond energy Si-O bonds in the existing lepidolite crystal skeleton are difficult to dissociate, resulting in low lithium ion extraction efficiency.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid comprises the following steps: S1, add activator to lepidolite concentrate, pre-activation treatment, obtain activated lepidolite concentrate powder; S2, mixing the lepidolite concentrate powder with a composite organic acid roasting agent, acidifying and roasting to obtain a roasted product; S3, adding water to the roasted product for leaching, and filtering to obtain a lithium-containing leachate; The composite organic acid roasting agent at least includes methanesulfonic acid.

[0008] According to the above technical means, by adding an activator to the lithium mica concentrate for pre-activation treatment, the surface properties of the lithium mica can be effectively improved, making it more sensitive to the subsequent acidification and roasting process, thereby improving the extraction efficiency of lithium. During the acidification and roasting process, the organic acid components such as methylsulfonic acid in the composite organic acid roasting agent can react chemically with the silicate structure in the lithium mica to generate soluble salts, thereby destroying the TOT layered structure of the lithium mica crystal and reducing its structural stability. At the same time, the participation of organic acid can also reduce the bond energy of the Si-O bond, so that it can dissociate at a lower temperature, thereby releasing the lithium ions locked in the lattice. This process not only solves the problem of low lithium ion extraction efficiency caused by the difficulty in destroying the lithium mica TOT layered structure and the difficulty in dissociating the high bond energy Si-O bond in the traditional method, but also reduces energy consumption and improves the lithium leaching rate through low-temperature roasting. It has significant economic benefits and environmental friendliness, and provides a new technical approach for the efficient utilization of lithium mica resources.

[0009] Preferably, the pre-activation treatment is to add the lepidolite concentrate to a Raymond mill, add an activator, control the spindle speed of the Raymond mill to 60-120 r / min, the moisture content of the material to 5-10%, and the Raymond mill pre-activation treatment time to 30-40 min to achieve pre-activation of the lepidolite concentrate.

[0010] Among them, the Raymond mill (suspension roller mill) refines the particles by squeezing and grinding the materials. The high-pressure shear force can break the Si-O-Al bond, increase the lattice defects, and provide channels for lithium ion diffusion. From the perspective of the reaction path, the effect of mechanical force can expose more interlayer K + / Li + sites to improve ion exchange efficiency. Therefore, in the process of Raymond milling, activators such as sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5) are added. The potassium ions (K + 、Na + ) and lithium ions (Li +) exchange occurs. Ion exchange helps to disrupt the layered structure of lepidolite, making it easier to leach later. Furthermore, during mechanical activation, metabisulfite is further oxidized to sulfate, ultimately yielding soluble lithium sulfate salts such as (K,Li)Al(SO4)2 and NaLiSO4. The transformation of weak acid salts into strong acid salts is more conducive to the release of hydrogen ions, which promotes the conversion and extraction of lithium during the roasting process. Therefore, the addition of an activator can reduce the reaction energy barrier of lepidolite concentrate under acidic conditions, allowing the lithium in the lepidolite to be effectively converted at lower temperatures and in shorter times. This effect is important for improving lithium leaching rates and reducing energy consumption.

[0011] Preferably, the activator is selected from one or both of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5).

[0012] Preferably, the activator is selected from sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5); The mass ratio of the lepidolite concentrate, sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5) is 1:0.1-0.3:0.1-0.2.

[0013] Preferably, the composite organic acid roasting agent further comprises one or both of tartaric acid and hexanoic acid.

[0014] Among them, compared with traditional sulfuric acid roasting, the composite organic acid roasting method of the present invention has the advantages of mild reaction conditions, low toxicity, and significantly reduced environmental risks. In addition, the organic acid selectively dissolves lithium through chelation, reducing the dissolution of impurities such as aluminum and iron. The sulfuric acid method results in a low comprehensive recovery rate of lithium, rubidium, and cesium (<50%) due to interference from impurities, while the mild reaction of organic acids may reduce the dissolution of associated metals, which is beneficial for subsequent comprehensive recovery. Therefore, the leachate after composite organic acid roasting has few impurities, which can shorten the purification process. A large amount of lime milk or NaOH is required to neutralize the residual acid after sulfuric acid roasting (1 ton of lithium carbonate consumes 0.8 to 1.2 tons of alkali), while the composite organic acid system of the present invention has lower alkali consumption.

[0015] During the calcination of lepidolite, methanesulfonic acid, tartaric acid, and hexanoic acid can also enhance the lithium ion extraction rate through ion exchange synergy. Specifically, methanesulfonic acid forms a stable complex with lithium ions, promoting their dissolution; while tartaric acid and hexanoic acid optimize lithium ion extraction conditions by adjusting the ionic strength of the solution and reducing the dissolution of other metal ions. This ion exchange synergy can significantly increase the lithium conversion rate. The mechanism of this synergy is as follows: 1) Mechanism of action of methanesulfonic acid Methanesulfonic acid (CH3SO3H) is a strong acid that can form a stable complex with lithium ions, thereby promoting the dissolution of lithium ions. During the roasting process, methanesulfonic acid can undergo an ion exchange reaction with the lithium ions in the lepidolite, releasing lithium ions from the solid phase and entering the liquid phase. This process can be expressed as: Among them, methanesulfonate ion (CH3SO3 － ) combines with lithium ions to form soluble lithium salts, thereby increasing the lithium extraction rate.

[0016] 2) Synergistic effect of tartaric acid and caproic acid Tartaric acid (C4H6O6) and hexanoic acid (C6H 13 During the roasting process, the presence of COOH (aluminum oxide) primarily optimizes lithium ion extraction conditions by adjusting the ionic strength of the solution. They form weak complexes with lithium ions but do not form stable complexes with most other metal ions (such as calcium, magnesium, and iron), thereby reducing the dissolution of these metal ions. This selective complexation helps further improve the purity and extraction rate of the lithium product.

[0017] The synergistic effect of tartaric acid and caproic acid is expressed as: The synergistic effect of the three acids is expressed as: Preferably, the composite organic acid roasting agent includes methanesulfonic acid, tartaric acid and hexanoic acid; The mass ratio of the lepidolite concentrate powder, methanesulfonic acid, tartaric acid and hexanoic acid is 1:0.5-0.8:0.2-0.4:0.3-0.5.

[0018] By combining methanesulfonic acid with tartaric acid and hexanoic acid for synergistic lithium extraction, the synergistic effect of strong and weak acids can improve reaction efficiency, adjust pH, and enhance reaction selectivity. Furthermore, the combination with organic acids can reduce equipment corrosion and facilitate biodegradation and recycling, with the degradation products being CO2 and water.

[0019] The specific principle of synergistic lithium extraction using composite organic acids is as follows: methanesulfonic acid, tartaric acid, and hexanoic acid achieve efficient lithium extraction during lithium extraction from lepidolite primarily through acidic synergy. The strong acidity of methanesulfonic acid disrupts the layered structure of lepidolite, promoting the release of lithium ions. Tartaric acid and hexanoic acid optimize the conditions for lithium ion replacement by adjusting the pH value. Furthermore, the strong acidity of methanesulfonic acid rapidly displaces the radical ions of weaker acids, generating more stable acids or salts, thereby improving reaction efficiency. This acidic synergy significantly increases lithium extraction yields.

[0020] Preferably, the purity of the methanesulfonic acid, tartaric acid and hexanoic acid is 99% or more, the amount of methanesulfonic acid is calculated based on the standard that 1 g of lepidolite concentrate requires 0.5 to 0.8 g of methanesulfonic acid, the amount of tartaric acid is calculated based on the standard that 1 g of lepidolite concentrate requires 0.2 to 0.4 g of tartaric acid, and the amount of hexanoic acid is calculated based on the standard that 1 g of lepidolite concentrate requires 0.3 to 0.5 g of hexanoic acid.

[0021] Preferably, the acidification and calcination is carried out in an autoclave, the temperature of the acidification and calcination is 100-300° C., the pressure of the acidification and calcination is 0.3-0.7 MPa, and the time of the acidification and calcination is 60-120 min.

[0022] Preferably, the temperature of the acidification roasting is 100-160°C.

[0023] Preferably, the acidification calcination in the autoclave is carried out in an inert atmosphere (such as argon or nitrogen) to prevent the organic acid from undergoing oxidation reaction at high temperature.

[0024] Methanesulfonic acid has a boiling point of 167°C and a decomposition temperature of 400°C; tartaric acid has a boiling point of 399.3°C and a decomposition temperature of 208°C; and hexanoic acid has a boiling point of 202-205°C and a decomposition temperature greater than 200°C. By using an autoclave to mix and roast the organic acid with lepidolite concentrate, the volatilization of the organic acid is effectively prevented, ensuring its stability and efficient reaction in the autoclave.

[0025] The principles of using autoclave roasting to prevent organic acid volatilization include: 1) Inert gas protection: by filling the autoclave with inert gas (such as argon or nitrogen), the oxidation reaction of organic acids at high temperatures is effectively prevented.

[0026] 2) Rapid cooling: After the reaction is completed, the autoclave is usually cooled quickly, which effectively prevents further volatilization of the organic acid at high temperature. Rapid cooling helps maintain the stability of the organic acid and prevents its loss during the cooling process.

[0027] 3) Sealing: The autoclave has good sealing performance, which can effectively prevent the escape of organic acids during the reaction process. The sealing ensures that the substances in the reaction system will not volatilize due to external interference, thereby improving the efficiency and safety of the reaction.

[0028] 4) Control of reaction conditions: By precisely controlling the reaction temperature, pressure, and time, the reaction process of the organic acid can be optimized, making it more stable in the autoclave.

[0029] Preferably, the leaching temperature is 90-99° C., and the leaching time is 60-90 min.

[0030] Preferably, the mass ratio of the roasted product to water is 1:3-5.

[0031] Preferably, the water is pure water.

[0032] Preferably, the chemical composition and mass percentage of the lepidolite concentrate are: LiO23.2 w / %, Al2O323.15 w / %, SiO255.22 w / %, Fe2O30.23 w / %, CaO 0.12 w / %, MgO 0.12 w / %, K2O 7.95 w / %, Na2O 2.88 w / %, TiO20.02 w / %, ZrO2<0.01 w / %, P2O50.34 w / %, SO3<0.05 w / %, F 4.82w / %, ZnO 0.04 w / %, SrO <0.01 w / %, MnO 0.27 w / %, NiO 0.03 w / %, CoO <0.01 w / %, CuO <0.01 w / %, Rb2O 1.01 w / %, BaO <0.05 w / %, Cs2O 0.16 w / %, the rest are other impurities.

[0033] Preferably, the method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid further comprises: S4, removing aluminum / fluorine impurities from the lithium-containing leachate through a precipitant to obtain a lithium-containing leachate after impurities removal; S5. The lithium-containing leachate after impurity removal is evaporated and concentrated, and then a lithium precipitation agent is added to carry out lithium precipitation reaction at room temperature and pressure, and filtered to obtain a lithium precipitate product and a residual filtrate.

[0034] Preferably, the precipitant is selected from at least one of calcium hydroxide, magnesium hydroxide, barium hydroxide and manganese hydroxide.

[0035] Preferably, the precipitating agent is selected from calcium hydroxide.

[0036] Preferably, the lithium precipitating agent is selected from carbonates.

[0037] Preferably, the lithium precipitating agent is selected from one or both of sodium carbonate and ammonium carbonate.

[0038] Preferably, the lithium precipitating agent is selected from sodium carbonate.

[0039] Preferably, the amount of sodium carbonate used is more than 4 times the mass of Li2O in the lithium-containing leachate after impurities removal.

[0040] Preferably, the method of removing aluminum / fluorine impurities by a precipitant is: adding a precipitant to the lithium-containing leachate to adjust the pH value of the lithium-containing leachate to above 12 to achieve the removal of aluminum / fluorine impurities.

[0041] Preferably, the volume of the solution after evaporation and concentration is 1 / 4 of the volume of the lithium-containing leachate after impurities removal.

[0042] The residual organic acids in the filtrate after lithium precipitation can be selectively adsorbed by a resin column to form methanesulfonate ions. After desorption, concentrated acid solution is obtained, enabling repeated recycling. Residual hexanoic acid and tartaric acid are easily degradable organic acids and can be biodegraded to produce CO2 and water, achieving zero emissions and significantly reducing environmental pollution.

[0043] Beneficial effects of the present invention: The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid of the present invention can effectively improve the surface properties of lepidolite by adding an activator to the lepidolite concentrate for pre-activation treatment, making it more sensitive to the subsequent acidification roasting process, thereby improving the extraction efficiency of lithium. During the acidification roasting process, the organic acid components such as methylsulfonic acid in the composite organic acid roasting agent can chemically react with the silicate structure in the lepidolite to generate soluble salts, thereby destroying the TOT layered structure of the lepidolite crystal and reducing its structural stability. At the same time, the participation of the organic acid can also reduce the bond energy of the Si-O bond, so that it can dissociate at a lower temperature, thereby releasing the lithium ions locked in the lattice. This process not only solves the problems of low lithium ion extraction efficiency caused by the difficulty in destroying the TOT layered structure of lithium mica and the difficulty in dissociating high-energy Si-O bonds in traditional methods, but also reduces energy consumption and improves the lithium leaching rate through low-temperature roasting. It has significant economic benefits and environmental friendliness, provides a new technical approach for the efficient utilization of lithium mica resources, is of great significance to the sustainable development of the lithium industry, and has promotion and application value in the field of lithium extraction technology from ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 These are the XRD patterns of lepidolite concentrate before and after activation. DETAILED DESCRIPTION

[0045] The following will describe the embodiments of the present invention with reference to preferred embodiments. Those skilled in the art will readily appreciate the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are intended only to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0046] If no specific techniques or conditions are specified in the specific examples, the techniques or conditions described in the literature in this field or the product instructions were used. If no manufacturer is specified for the reagents or instruments used, they are all commercially available conventional products.

[0047] In the following examples and comparative examples, the chemical composition and mass percentage of the lepidolite concentrate used are: LiO23.2 w / %, Al2O323.15 w / %, SiO255.22 w / %, Fe2O30.23 w / %, CaO 0.12 w / %, MgO 0.12w / %, K2O 7.95 w / %, Na2O 2.88 w / %, TiO20.02 w / %, ZrO2<0.01 w / %, P2O50.34 w / %, SO3<0.05 w / %, F 4.82 w / %, ZnO 0.04 w / %, SrO <0.01 w / %, MnO 0.27 w / %, NiO 0.03 w / %, CoO<0.01 w / %, CuO <0.01 w / %, Rb2O 1.01 w / %, BaO <0.05 w / %, Cs2O 0.16 w / %, and the remainder are other impurities. F primarily exists in the form of MeF·MeOH·Al2O3·3SiO2, and Me represents alkali metal elements such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

[0048] Example 1 A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid comprises the following steps: S1, 1000 g of lepidolite concentrate was added to a Raymond mill, followed by the addition of 200 g of sodium metabisulfite (Na2S2O5), an activator, the spindle speed of the Raymond mill was controlled to 80 r / min, the material moisture content was 6%, and the Raymond mill was pre-activated for 30 min to obtain activated lepidolite concentrate powder; S2, the lepidolite concentrate powder obtained in S1 is evenly mixed with a composite organic acid roasting agent, and then placed in an autoclave, followed by acidification roasting for 60 min at a temperature of 130° C. and a pressure of 0.3 MPa to obtain a roasted product; wherein the composite organic acid roasting agent comprises 99% methanesulfonic acid and tartaric acid; the mass ratio of the lepidolite concentrate powder, 99% methanesulfonic acid, and tartaric acid is 1:0.6:0.4; S3, mixing the roasted product obtained in S2 with pure water in a mass ratio of 1:4, then stirring and leaching in a water bath at a temperature of 90° C. for 60 min, and filtering to obtain a lithium-containing leachate and a leach residue; S4, adding Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities by the precipitant, and obtain a lithium-containing leachate after impurity removal; S5. The lithium-containing leachate after impurity removal was evaporated and concentrated 4 times, and then 125 g of sodium carbonate lithium precipitation agent was added to carry out lithium precipitation reaction, and the lithium carbonate product and the remaining filtrate were obtained by filtration.

[0049] Example 2 A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid comprises the following steps: S1, 1000 g of lepidolite concentrate was added to a Raymond mill, followed by the addition of 200 g of potassium metabisulfite (K2S2O5), an activator, the spindle speed of the Raymond mill was controlled to be 100 r / min, the material moisture content was 5%, and the Raymond mill was pre-activated for 30 min to obtain activated lepidolite concentrate powder; S2, the lepidolite concentrate powder obtained in S1 is evenly mixed with a composite organic acid roasting agent and placed in an autoclave, and then acidified and roasted for 90 min at a temperature of 150° C. and a pressure of 0.5 MPa to obtain a roasted product; wherein the composite organic acid roasting agent comprises methylsulfonic acid and hexanoic acid with a concentration of 99%; the mass ratio of the lepidolite concentrate powder, methylsulfonic acid with a concentration of 99% and hexanoic acid is 1:0.5:0.5; S3, mixing the roasted product obtained in S2 with pure water in a mass ratio of 1:4, then stirring and leaching in a water bath at a temperature of 95° C. for 80 min, and filtering to obtain a lithium-containing leachate and a leach residue; S4, adding Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities by the precipitant, and obtain a lithium-containing leachate after impurity removal; S5. The lithium-containing leachate after impurity removal was evaporated and concentrated 4 times, and then 130 g of sodium carbonate lithium precipitation agent was added to carry out lithium precipitation reaction, and the lithium carbonate product and the remaining filtrate were obtained by filtration.

[0050] Example 3 A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid comprises the following steps: S1. 1000 g of lepidolite concentrate was added to a Raymond mill, followed by the addition of 200 g of a mixture of activators, sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5), the spindle speed of the Raymond mill was controlled to be 120 r / min, the moisture content of the material was 7%, and the Raymond mill was pre-activated for 35 min to obtain activated lepidolite concentrate powder; wherein the mass ratio of lepidolite concentrate, sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5) was 1:0.1:0.1; S2, the lepidolite concentrate powder obtained in S1 is evenly mixed with a composite organic acid roasting agent and placed in an autoclave, and then acidified and roasted for 120 min at a temperature of 160° C. and a pressure of 0.7 MPa to obtain a roasted product; wherein the composite organic acid roasting agent comprises 99% methanesulfonic acid, tartaric acid and hexanoic acid; the mass ratio of the lepidolite concentrate powder, 99% methanesulfonic acid, tartaric acid and hexanoic acid is 1:0.5:0.2:0.3; S3, mixing the roasted product obtained in S2 with pure water in a mass ratio of 1:4, then stirring and leaching in a water bath at a temperature of 95° C. for 90 min, and filtering to obtain a lithium-containing leachate and a leach residue; S4, adding Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities by the precipitant, and obtain a lithium-containing leachate after impurity removal; S5. The lithium-containing leachate after impurity removal was evaporated and concentrated 4 times, and then 135 g of sodium carbonate lithium precipitation agent was added to carry out lithium precipitation reaction, and the lithium carbonate product and the remaining filtrate were obtained by filtration.

[0051] Comparative Example 1 A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid comprises the following steps: S1. 1000 g of lepidolite concentrate powder and a composite organic acid roasting agent were uniformly mixed and placed in an autoclave, and then acidified and roasted for 120 min at a temperature of 160 ° C. and a pressure of 0.7 MPa to obtain a roasted product; wherein the composite organic acid roasting agent includes methylsulfonic acid, tartaric acid and hexanoic acid with a concentration of 99%; the mass ratio of the lepidolite concentrate powder, methylsulfonic acid with a concentration of 99%, tartaric acid and hexanoic acid is 1:0.5:0.2:0.3; S2, mixing the roasted product obtained in S1 with pure water in a mass ratio of 1:4, then stirring and leaching in a water bath at a temperature of 95° C. for 90 min, and filtering to obtain a lithium-containing leachate and a leach residue; S3, adding Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities by the precipitant, and obtain a lithium-containing leachate after impurity removal; S4. The lithium-containing leachate after impurity removal was evaporated and concentrated 4 times, and then 135 g of sodium carbonate lithium precipitation agent was added to carry out lithium precipitation reaction, and the lithium carbonate product and the remaining filtrate were obtained by filtration.

[0052] Comparative Example 2 A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid comprises the following steps: S1. 1000 g of lepidolite concentrate was added to a Raymond mill, followed by the addition of 200 g of a mixture of activators, sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5), the spindle speed of the Raymond mill was controlled to be 120 r / min, the moisture content of the material was 7%, and the Raymond mill was pre-activated for 35 min to obtain activated lepidolite concentrate powder; wherein the mass ratio of lepidolite concentrate, sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5) was 1:0.1:0.1; S2, the lepidolite concentrate powder obtained in S1 is evenly mixed with an organic acid roasting agent and placed in an autoclave, and then acidified and roasted for 120 min at a temperature of 160° C. and a pressure of 0.7 MPa to obtain a roasted product; wherein the organic acid roasting agent is methylsulfonic acid with a concentration of 99%; and the mass ratio of the lepidolite concentrate powder to the methylsulfonic acid with a concentration of 99% is 1:0.8; S3, mixing the roasted product obtained in S2 with pure water in a mass ratio of 1:5, and then stirring and leaching for 90 min in a water bath at a temperature of 95° C., and filtering to obtain a lithium-containing leachate and a leach residue; S4, adding Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities by the precipitant, and obtain a lithium-containing leachate after impurity removal; S5. The lithium-containing leachate after impurity removal was evaporated and concentrated 4 times, and then 135 g of sodium carbonate lithium precipitation agent was added to carry out lithium precipitation reaction, and the lithium carbonate product and the remaining filtrate were obtained by filtration.

[0053] Comparative Example 3 The traditional lithium extraction process of lepidolite by high-temperature sulfuric acid roasting includes the following steps: S1, 1000 g of lepidolite concentrate powder is mixed with 98% concentrated sulfuric acid, then placed in a muffle furnace, and carried out acidification roasting 120 min under the condition of 800 ℃ to obtain a roasted product; wherein, the mass ratio of the lepidolite concentrate powder to the 98% concentrated sulfuric acid is 1:0.8; S2, mixing the roasted product obtained in S1 with pure water in a mass ratio of 1:5, and then stirring and leaching for 90 min in a water bath at a temperature of 95° C., and filtering to obtain a lithium-containing leachate and a leach residue; S3, adding Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities by the precipitant, and obtain a lithium-containing leachate after impurity removal; S4. The lithium-containing leachate after impurity removal was evaporated and concentrated 4 times, and then 135 g of sodium carbonate lithium precipitation agent was added to carry out lithium precipitation reaction, and the lithium precipitate product and filtrate were obtained by filtration.

[0054] Detection and Analysis 1) Determination of Li2O content in leached residue, pH value of lithium-containing leachate, leached residue yield, and Li2O leaching rate in lepidolite concentrate The calculation formula for the Li2O leaching rate in lepidolite concentrate is: lithium leaching rate = [leachate volume (L) × lithium oxide concentration in leachate (g / L)] / [lithium oxide content in lepidolite concentrate (%) × lepidolite concentrate mass (g)] × 100% Yield of leaching residue (%) = [100% × dry weight of leaching residue (g)] / dry weight of lepidolite concentrate powder (g) The results are shown in Table 1.

[0055] Table 1 shows the results of the determination of lithium-containing leachate and leach residue From the analysis in Table 1, it can be seen that by pre-activating the lepidolite concentrate by combining a Raymond mill and an activator, and then using a mixture of 99% methanesulfonic acid and one or two of tartaric acid and hexanoic acid as a composite organic acid roasting agent for roasting in an autoclave, and then through the leaching reaction, the Li2O leaching rate can be made above 95%. By comparing Example 3 and Comparative Example 1, it can be seen that when the lepidolite concentrate is pre-activated by using a Raymond mill and an activator, the leaching rate of Li2O in the leachate is increased by 15.47% compared with that of the unactivated one; the yield of lithium slag is reduced by 9.48%; by comparing Example 3 and Comparative Example 2, it can be seen that when 99% methanesulfonic acid, tartaric acid and hexanoic acid are used as a composite roasting agent, the leaching rate of Li2O in the leachate is increased by 11.43% compared with that of 99% methanesulfonic acid alone as a roasting agent, and the yield of lithium slag is reduced by 20.11%; by comparing Example 3 and Comparative Example 3, it can be seen that when the lepidolite concentrate is pre-activated by using a Raymond mill and an activator, and 99% methanesulfonic acid, tartaric acid and hexanoic acid are used as a composite roasting agent, the leaching rate of Li2O in the leachate is increased by 23.3% compared with the leaching rate of the traditional sulfuric acid 800°C high-temperature roasting process, and the yield of lithium slag is reduced by 24.39%. This demonstrates that the novel process of low-temperature roasting using a composite organic acid method in the present invention significantly improves the leaching rate of Li2O, reduces the amount of slag, and can achieve the conversion of lithium in lepidolite at a lower temperature, thereby saving energy consumption and reducing production costs.

[0056] 2) XRD test The lepidolite concentrate powder in S1 of Example 3 that was pre-activated by Raymond mill and mixed activator of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5) and the lepidolite concentrate powder before activation were dried and sampled, and then XRD test was performed. The results are as follows: Figure 1 shown.

[0057] Figure 1In the figure, the powder before activation corresponds to the lepidolite concentrate powder before activation, and the powder after activation corresponds to the lepidolite concentrate powder that has been pre-activated by Raymond mill and a mixed activator of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5).

[0058] from Figure 1 Comparative analysis before and after activation shows that the diffraction peaks of unactivated lithium mica concentrate are mostly feldspar, mica and silica phases. After activation by Raymond mill and activator metabisulfite, new diffraction peaks of soluble lithium sulfate product were observed. This proves that the potassium ion (K + ) sodium ion (Na + ) and lithium ions (Li + ) exchange occurs, altering the crystal structure of the lepidolite. Simultaneously, during mechanical activation, the activator undergoes a solid-phase reaction with the lepidolite, generating soluble intermediates such as (K,Li)Al(SO4)2 and NaLiSO4. The formation of these intermediates not only contributes to the structural breakdown of the lepidolite but also promotes the conversion and extraction of lithium during the calcination process.

[0059] 3) Determination of leachate composition The lithium-containing leachate obtained in S3 of Example 3 and the lithium-containing leachate obtained in S2 of Comparative Example 3 were analyzed for composition using inductively coupled plasma emission spectrometry (ICP), gas chromatography-mass spectrometry (GC-MS), atomic absorption spectrophotometry (AAS), and automated potentiometric titration. The results are shown in Tables 2 and 3.

[0060] Table 2 shows the main components of the lithium-containing leachate obtained in Example 3 Note: The organic acid ion is methanesulfonate ion CH3SO3 － , tartrate ion C4H4O6 2- and hexanoate ion C6H 13 COO − .

[0061] Table 3 shows the main components of the lithium-containing leachate obtained in Comparative Example 3 Table 2 shows that the Li concentration in the calcined leachate is 7.85 g / L. The main impurities include Ca, Al, Fe, SiO2, and F. Other impurities include Mg, Mn, and other elements. Compared with the traditional sulfuric acid method (Table 3), the Ca, Fe, and F contents are less than 0.1 g / L, the Al content is reduced by 31.2%, and the SiO2 content is reduced by 59.4%. The contents of other impurities are less than 0.01 g / L. This fully demonstrates that the mild reaction of organic acids reduces the dissolution of impurities and largely ensures the purity of the subsequent product.

[0062] In summary, the method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid of the present invention, by adding an activator to the lepidolite concentrate for pre-activation treatment, can effectively improve the surface properties of lepidolite, making it more sensitive to the subsequent acidification roasting process, thereby improving the extraction efficiency of lithium. During the acidification roasting process, the organic acid components such as methylsulfonic acid in the composite organic acid roasting agent can chemically react with the silicate structure in the lepidolite to generate soluble salts, thereby destroying the TOT layered structure of the lepidolite crystal and reducing its structural stability. At the same time, the participation of the organic acid can also reduce the bond energy of the Si-O bond, so that it can dissociate at a lower temperature, thereby releasing the lithium ions locked in the lattice. This process not only solves the problem that the TOT layered structure of lepidolite is difficult to destroy and the high bond energy Si-O bond is difficult to dissociate in the traditional method, resulting in low lithium ion extraction efficiency, but also reduces energy consumption and improves the leaching rate of lithium by low-temperature roasting, has significant economic benefits and environmental friendliness, and provides a new technical approach for the efficient utilization of lepidolite resources. Compared with the sulfuric acid method alone, this method effectively increases the conversion rate of lithium in lepidolite, while also reducing the roasting temperature and saving energy. Furthermore, while the sulfuric acid method alone is highly adaptable to raw materials, it produces a large amount of waste residue. The synergistic effect of the activator and the composite organic acid effectively reduces the amount of waste residue and reduces environmental pollution. This is of great significance to the sustainable development of the lithium industry and has great application value in the field of lithium extraction technology from ores.

[0063] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid, characterized in that: The following steps are involved: S1, add activator to lepidolite concentrate, pre-activation treatment, obtain activated lepidolite concentrate powder; S2, mixing the lepidolite concentrate powder with a composite organic acid roasting agent, acidifying and roasting to obtain a roasted product; S3, adding water to the roasted product for leaching to obtain a lithium-containing leachate; The composite organic acid roasting agent at least includes methanesulfonic acid.

2. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 1, characterized in that: The pre-activation treatment is to add the lepidolite concentrate into a Raymond mill, add an activator, control the Raymond mill spindle speed to 60-120 r / min, the material moisture content to 5-10%, and the Raymond mill pre-activation treatment time to 30-40 min to achieve pre-activation of the lepidolite concentrate.

3. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 2, characterized in that: The activator is selected from one or both of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5).

4. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 3, characterized in that: The activator is selected from sodium metabisulfite and potassium metabisulfite; The mass ratio of the lepidolite concentrate, sodium metabisulfite and potassium metabisulfite is 1:0.1-0.3:0.1-0.

2.

5. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 1, characterized in that: The composite organic acid roasting agent further comprises one or both of tartaric acid and hexanoic acid.

6. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 5, characterized in that: The composite organic acid roasting agent includes methanesulfonic acid, tartaric acid and hexanoic acid; The mass ratio of the lepidolite concentrate powder, methanesulfonic acid, tartaric acid and hexanoic acid is 1:0.5-0.8:0.2-0.4:0.3-0.

5.

7. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 1, characterized in that: The acidification and calcination is carried out in an autoclave at a temperature of 100-300°C, a pressure of 0.3-0.7 MPa, and a time of 60-120 min. and / or, the leaching temperature is 90-99° C., and the leaching time is 60-90 min; And / or, the mass ratio of the roasted product to water is 1:3-5.

8. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 1, characterized in that: The chemical composition and mass percentage of the lepidolite concentrate are as follows: LiO2 3.2 w / %, Al2O3 23.15 w / %, SiO2 55.22 w / %, Fe2O3 0.23 w / %, CaO 0.12 w / %, MgO 0.12 w / %, K2O 7.95 w / %, Na2O 2.88 w / %, TiO2 0.02 w / %, ZrO2 <0.01 w / %, P2O5 0.34 w / %, SO3 <0.05 w / %, F 4.82 w / %, ZnO 0.04 w / %, SrO <0.01 w / %, MnO 0.27 w / %, NiO 0.03 w / %, CoO <0.01 w / %, CuO <0.01 w / %, Rb2O 1.01 w / %, BaO <0.05 w / %, Cs2O 0.16 w / %, the rest are other impurities.

9. A method for efficiently extracting lithium from lepidolite by low-temperature roasting of a composite organic acid according to any one of claims 1 to 8, characterized in that: Also includes: S4, removing aluminum / fluorine impurities from the lithium-containing leachate through a precipitant to obtain a lithium-containing leachate after impurities removal; S5. The lithium-containing leachate after impurity removal is evaporated and concentrated, and then a lithium precipitation agent is added to carry out lithium precipitation reaction at room temperature and pressure, and filtered to obtain a lithium precipitate product and a residual filtrate.

10. The method for efficiently extracting lithium from lepidolite by low-temperature roasting of composite organic acid according to claim 9, characterized in that: The precipitant is selected from at least one of calcium hydroxide, magnesium hydroxide, barium hydroxide and manganese hydroxide; And / or, the lithium precipitating agent is selected from carbonates.

Images