Method for efficiently extracting lithium from lepidolite by low-temperature calcination with composite organic acid

Abstract

The present application relates to a kind of composite organic acid low-temperature calcination lepidolite high-efficiency lithium extraction method.Composite organic acid low-temperature calcination lepidolite high-efficiency lithium extraction method includes the following steps: adding activating agent to lepidolite concentrate, pre-activation treatment, obtain the activated lepidolite concentrate powder;Lepidolite concentrate powder is mixed with composite organic acid calcining agent acidification calcination, obtain the calcination product;Water is added to the calcination product and leaching, suction filtration, obtain the lithium-containing leaching solution;Composite organic acid calcining agent at least includes methyl sulfonic acid.The present application solves the problem that TOT layered structure in lepidolite is difficult to destroy, resulting in low lithium ion extraction efficiency, also solves the problem that Si-O bond in the existing lepidolite crystal framework is difficult to dissociate, resulting in low lithium ion extraction efficiency.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from ores, specifically to a method for efficient lithium extraction from lepidolite by low-temperature roasting with composite organic acids. Background Technology

[0002] Lithium, as an important strategic resource, has crucial applications in many fields such as new energy, electronic information, and aerospace. In particular, with the rapid development of industries such as electric vehicles and energy storage batteries, the demand for lithium is showing a continuous upward trend. Lithium mica, as a mineral resource rich in lithium, has enormous development potential.

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

[0004] In the crystal structure of lepidolite, Al 3+ Isomorphic substitution of Si will occur 4+ This leads to an imbalance of charge across the entire interlayer. To maintain charge balance, Li... + K + Alkali metal ions will embed themselves within it to compensate. In this way, lithium ions are locked inside the stable silicate lattice and cannot be released freely. To extract lithium ions 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 constituting the crystal framework of lepidolite, with a high bond energy of 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, breaking its stable TOT layered structure while overcoming the obstacle posed by the high bond energy of the Si-O bond, has become a pressing technical challenge in the 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 high-efficiency lithium extraction from lepidolite by low-temperature calcination of composite organic acids, 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 framework are difficult to dissociate, resulting in low lithium ion extraction efficiency.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for efficient lithium extraction from lepidolite by low-temperature calcination of composite organic acids includes the following steps:

[0009] S1. Add an activator to the lepidolite concentrate for pre-activation treatment to obtain activated lepidolite concentrate powder.

[0010] S2. Mix lithium mica concentrate powder with a composite organic acid roasting agent, acidify and roast to obtain roasted product;

[0011] S3. Add water to the roasted product for extraction, filter, and obtain lithium-containing leachate;

[0012] The composite organic acid calcining agent includes at least methanesulfonic acid.

[0013] Based on the aforementioned technical methods, pre-activation treatment of lepidolite concentrate by adding an activator can effectively improve the surface properties of lepidolite, making it more sensitive to subsequent acid roasting processes and thus improving lithium extraction efficiency. During acid roasting, the organic acid components, such as methanesulfonic acid, in the composite organic acid roasting agent can chemically react with the silicate structure in lepidolite to generate soluble salts, thereby destroying the TOT layered structure of the lepidolite crystal and reducing its structural stability. Simultaneously, the participation of organic acids can also reduce the bond energy of Si-O bonds, allowing them to dissociate at lower temperatures, thus releasing lithium ions locked in the crystal 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 lepidolite and the difficulty in dissociating high-bond-energy Si-O bonds in traditional methods, but also reduces energy consumption and increases lithium leaching rate through low-temperature roasting, demonstrating significant economic benefits and environmental friendliness, and providing a new technical approach for the efficient utilization of lepidolite resources.

[0014] Preferably, the pre-activation treatment involves adding lepidolite concentrate to a Raymond mill, adding an activator, controlling 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, in order to achieve pre-activation of the lepidolite concentrate.

[0015] Among them, the Raymond mill (suspension roller mill) refines particles through the extrusion and grinding between materials. High-pressure shearing force can break Si-O-Al bonds, increasing lattice defects and providing channels for lithium-ion diffusion. From the reaction pathway perspective, the mechanical force can expose more interlayer K+. + / Li + This improves ion exchange efficiency by creating sites for ion exchange. Therefore, sodium metabisulfite (Na₂S₂O₅) and potassium metabisulfite (K₂S₂O₅) are added as activators during the Raymond milling process. The potassium ions in the activators (K₂S₂O₅) enhance the ion exchange efficiency.+ Na + ) and lithium ions (Li) in lepidolite + An ion exchange reaction occurs, which helps to disrupt the layered structure of lepidolite, making it easier to leach. Furthermore, during mechanical activation, metabisulfite is further oxidized to sulfate, ultimately yielding soluble lithium sulfate products such as (K,Li)Al(SO4)2 and NaLiSO4. This transformation from a weak acid salt to a strong acid salt is more conducive to the release of hydrogen ions, promoting the conversion and extraction of lithium during roasting. Therefore, the addition of an activator can lower the reaction energy barrier of lepidolite concentrate under acidic conditions, allowing lithium in lepidolite to be effectively converted at lower temperatures and in a shorter time. This effect is significant for improving lithium leaching rates and reducing energy consumption.

[0016] Preferably, the activator is selected from one or both of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5).

[0017] Preferably, the activator is selected from sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5).

[0018] The mass ratio of the lepidolite concentrate, sodium metabisulfite (Na2S2O5), and potassium metabisulfite (K2S2O5) is 1:0.1~0.3:0.1~0.2.

[0019] Preferably, the composite organic acid roasting agent further includes one or both of tartaric acid and hexanoic acid.

[0020] Compared to traditional sulfuric acid roasting, the composite organic acid roasting method of this invention has advantages such as milder reaction conditions, lower toxicity, and significantly reduced environmental risks. Furthermore, the organic acid selectively dissolves lithium through chelation, reducing the leaching of impurities such as aluminum and iron. The sulfuric acid method suffers from low overall lithium, rubidium, and cesium recovery rates (<50%) due to impurity interference, while the mild reaction of the organic acid may reduce the leaching of associated metals, facilitating subsequent comprehensive recovery. Therefore, the leachate after composite organic acid roasting has fewer impurities, shortening the purification process. Neutralizing residual acid after sulfuric acid roasting requires a large amount of lime milk or NaOH (0.8~1.2 tons of alkali per ton of lithium carbonate), while the composite organic acid system of this invention consumes even less alkali.

[0021] During the calcination of lepidolite, methanesulfonic acid, tartaric acid, and hexanoic acid can enhance lithium ion extraction through synergistic ion exchange. Specifically, methanesulfonic acid can form stable complexes with lithium ions, promoting their dissolution; tartaric acid and hexanoic acid can optimize lithium ion extraction conditions and reduce the dissolution of other metal ions by adjusting the ionic strength of the solution. This synergistic effect can significantly improve lithium conversion. The mechanism of this synergistic effect is as follows:

[0022] 1) Mechanism of action of methanesulfonic acid

[0023] Methylsulfonic acid (CH3SO3H) is a strong acid that can form stable complexes with lithium ions, thereby promoting the dissolution of lithium ions. During calcination, methylsulfonic acid can undergo an ion exchange reaction with lithium ions in lepidolite, releasing the lithium ions from the solid phase into the liquid phase. This process can be represented as follows:

[0024]

[0025] Among them, methanesulfonate ions (CH3SO3) － It combines with lithium ions to form soluble lithium salts, thereby increasing the lithium extraction rate.

[0026] 2) Synergistic effect of tartaric acid and hexanoic acid

[0027] Tartaric acid (C4H6O6) and hexanoic acid (C6H 13 During the roasting process, COOH groups primarily optimize lithium ion extraction conditions by adjusting the ionic strength of the solution. They can form weak complexes with lithium ions but do not form stable complexes with most other metal ions (such as calcium, magnesium, and iron), thus reducing the dissolution of these metal ions. This selective complexation helps to further improve the purity and extraction rate of lithium products.

[0028] The synergistic effect of tartaric acid and hexanoic acid is expressed as follows:

[0029]

[0030] The synergistic effect of the three acids is represented as follows:

[0031]

[0032] Preferably, the composite organic acid calcining agent includes methanesulfonic acid, tartaric acid, and hexanoic acid;

[0033] 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.

[0034] By using a combination of methanesulfonic acid, tartaric acid, and hexanoic acid for synergistic lithium extraction, the synergistic effect of strong and weak acids can improve reaction efficiency, adjust pH value, and enhance reaction selectivity. Furthermore, the combination of organic acids can reduce equipment corrosion, facilitate biodegradation and recycling, and the degradation products are CO2 and water.

[0035] The specific principle of synergistic lithium extraction using compound organic acids is as follows: In the lithium extraction process from lepidolite, methanesulfonic acid, tartaric acid, and hexanoic acid primarily achieve efficient lithium extraction through acidic synergistic effects. The strong acidity of methanesulfonic acid can disrupt the layered structure of lepidolite, promoting the release of lithium ions; tartaric acid and hexanoic acid optimize the lithium ion replacement conditions by adjusting the pH value. Furthermore, the strong acidity of methanesulfonic acid can rapidly displace the anions of weak acids, generating more stable acids or salts, thereby improving reaction efficiency. This acidic synergistic effect can significantly improve the lithium extraction rate.

[0036] Preferably, the purity of the methanesulfonic acid, tartaric acid, and hexanoic acid is all above 99%. The amount of methanesulfonic acid is calculated based on the standard that 0.5~0.8 g of methanesulfonic acid is needed per g of lepidolite concentrate, the amount of tartaric acid is calculated based on the standard that 0.2~0.4 g of tartaric acid is needed per g of lepidolite concentrate, and the amount of hexanoic acid is calculated based on the standard that 0.3~0.5 g of hexanoic acid is needed per g of lepidolite concentrate.

[0037] Preferably, the acidification roasting is carried out in a high-pressure autoclave, the acidification roasting temperature is 100~300 ℃, the acidification roasting pressure is 0.3~0.7 MPa, and the acidification roasting time is 60~120 min.

[0038] Preferably, the acidification and roasting temperature is 100~160 ℃.

[0039] Preferably, the acid roasting in the autoclave is carried out in an inert atmosphere (such as argon or nitrogen) to prevent the organic acids from undergoing oxidation at high temperatures.

[0040] Methanesulfonic acid has a boiling point of 167 ℃ and a decomposition temperature of 400 ℃; tartaric acid has a boiling point of 399.3 ℃ and a decomposition temperature of 208 ℃; and hexanoic acid has a boiling point of 202~205 ℃ and a decomposition temperature greater than 200 ℃. By using an autoclave for the mixed roasting of organic acids and lepidolite concentrate, the volatilization of the organic acids was effectively prevented, ensuring the stability and efficient reaction of the organic acids in the autoclave.

[0041] The principle of using an autoclave to prevent the volatilization of organic acids includes:

[0042] 1) Inert gas protection: By filling the autoclave with an inert gas (such as argon or nitrogen), the oxidation reaction of organic acids at high temperatures is effectively prevented.

[0043] 2) Rapid cooling: After the reaction is complete, the autoclave is usually cooled rapidly to effectively prevent further volatilization of the organic acids at high temperatures. Rapid cooling helps maintain the stability of the organic acids and prevents their loss during the cooling process.

[0044] 3) Sealing performance: The autoclave has excellent sealing performance, which can effectively prevent organic acids from escaping during the reaction. This sealing ensures that substances within the reaction system will not volatilize due to external interference, thereby improving the efficiency and safety of the reaction.

[0045] 4) Reaction condition control: By precisely controlling the reaction temperature, pressure and time, the reaction process of organic acids can be optimized, making them more stable in the autoclave.

[0046] Preferably, the immersion temperature is 90~99 ℃ and the immersion time is 60~90 min.

[0047] Preferably, the mass ratio of the roasted product to water is 1:3~5.

[0048] Preferably, the water is pure water.

[0049] Preferably, 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 remainder being other impurities.

[0050] Preferably, the method for high-efficiency lithium extraction from lepidolite by low-temperature calcination of composite organic acids further includes:

[0051] S4. The lithium-containing leachate is passed through a precipitant to remove aluminum / fluorine impurities, resulting in a purified lithium-containing leachate.

[0052] S5. Evaporate and concentrate the lithium-containing leachate after impurity removal, then add a lithium precipitation agent to carry out a lithium precipitation reaction at room temperature and pressure, filter, and obtain lithium precipitate product and remaining filtrate.

[0053] Preferably, the precipitant is selected from at least one of calcium hydroxide, magnesium hydroxide, barium hydroxide, and manganese hydroxide.

[0054] Preferably, the precipitant is selected from calcium hydroxide.

[0055] Preferably, the lithium precipitation agent is selected from carbonates.

[0056] Preferably, the lithium precipitation agent is selected from one or both of sodium carbonate and ammonium carbonate.

[0057] Preferably, the lithium precipitation agent is selected from sodium carbonate.

[0058] Preferably, the amount of sodium carbonate used is more than four times the mass of Li2O in the lithium-containing leachate after impurity removal.

[0059] Preferably, the method of removing aluminum / fluorine impurities by using a precipitant is as follows: by adding a precipitant to the lithium-containing leachate to adjust the pH value of the lithium-containing leachate to above 12, the aluminum / fluorine impurities are removed.

[0060] Preferably, the volume of the solution after evaporation and concentration is 1 / 4 of the volume of the lithium-containing leachate after impurity removal.

[0061] The residual organic acids in the filtrate after lithium precipitation can be selectively adsorbed by a resin column to obtain concentrated acid solution after desorption, thus achieving repeated recycling. The residual hexanoic acid and tartaric acid are easily degradable organic acids and can be biodegraded to ultimately produce CO2 and water, achieving zero emissions and greatly reducing environmental pollution.

[0062] The beneficial effects of this invention are:

[0063] The present invention discloses a method for high-efficiency lithium extraction from lepidolite through low-temperature roasting with composite organic acids. By adding an activator to the lepidolite concentrate for pre-activation treatment, the surface properties of lepidolite are effectively improved, making it more sensitive to subsequent acid roasting processes, thereby increasing lithium extraction efficiency. During the acid roasting process, the organic acid components, such as methanesulfonic acid, in the composite organic acid roasting agent can chemically react with the silicate structure in lepidolite to generate soluble salts, thereby disrupting the TOT layered structure of the lepidolite crystal and reducing its structural stability. Simultaneously, the participation of organic acids can also reduce the bond energy of the Si-O bonds, allowing them to dissociate at lower temperatures, thus releasing lithium ions locked in the crystal lattice. This process not only solves the problems of low lithium-ion extraction efficiency caused by the difficulty in destroying the layered structure of lepidolite TOT and the difficulty in dissociating high bond energy Si-O bonds in traditional methods, but also reduces energy consumption and improves lithium leaching rate through low-temperature roasting. It has significant economic benefits and environmental friendliness, and provides a brand-new technical approach for the efficient utilization of lepidolite resources. It is of great significance to the sustainable development of the lithium industry and has promotion and application value in the field of lithium extraction from ore. Attached Figure Description

[0064] Figure 1 The images show the XRD patterns of lepidolite concentrate before and after activation. Detailed Implementation

[0065] The following description, with reference to preferred embodiments, illustrates the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are merely illustrative of the present invention and not intended to limit the scope of protection of the present invention.

[0066] Where specific techniques or conditions are not specified in the detailed embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0067] In the following examples and comparative examples, the chemical composition and mass percentage of the lepidolite concentrate used were 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 The content of F is 0.16 w / %, Cs2O is 0.16 w / %, and the remainder is other impurities. Among them, F mainly 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).

[0068] Example 1

[0069] A method for efficient lithium extraction from lepidolite by low-temperature calcination of composite organic acids includes the following steps:

[0070] S1. Add 1000 g of lepidolite concentrate to a Raymond mill, then add 200 g of activator sodium metabisulfite (Na2S2O5), control the Raymond mill spindle speed to 80 r / min, the material moisture content to 6%, and pre-activate the Raymond mill for 30 min to obtain activated lepidolite concentrate powder.

[0071] S2. The lithium mica concentrate powder obtained in S1 is mixed evenly with the composite organic acid roasting agent and placed in a high-pressure autoclave. Then, it is acidified and roasted for 60 min at a temperature of 130 ℃ and a pressure of 0.3 MPa to obtain the roasted product. The composite organic acid roasting agent includes 99% methanesulfonic acid and tartaric acid. The mass ratio of lithium mica concentrate powder, 99% methanesulfonic acid and tartaric acid is 1:0.6:0.4.

[0072] S3. The roasted product obtained in S2 is mixed with pure water at a mass ratio of 1:4, and then stirred and leached for 60 min under a water bath at a temperature of 90 ℃. After filtration, lithium-containing leachate and leaching residue are obtained.

[0073] S4. Add Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities with the precipitant and obtain the lithium-containing leachate after impurity removal.

[0074] S5. Evaporate and concentrate the lithium-containing leachate after impurity removal by 4 times, then add 125 g of sodium carbonate lithium precipitation agent to carry out the lithium precipitation reaction, and filter to obtain lithium carbonate product and remaining filtrate.

[0075] Example 2

[0076] A method for efficient lithium extraction from lepidolite by low-temperature calcination of composite organic acids includes the following steps:

[0077] S1. Add 1000 g of lepidolite concentrate to a Raymond mill, then add 200 g of activator potassium metabisulfite (K2S2O5), control the Raymond mill spindle speed to 100 r / min, the material moisture content to 5%, and pre-activate the Raymond mill for 30 min to obtain activated lepidolite concentrate powder.

[0078] S2. The lithium mica concentrate powder obtained in S1 is mixed evenly with the composite organic acid roasting agent and placed in a high-pressure autoclave. Then, it is acidified and roasted for 90 min at a temperature of 150 ℃ and a pressure of 0.5 MPa to obtain the roasted product. The composite organic acid roasting agent includes 99% methanesulfonic acid and hexanoic acid. The mass ratio of lithium mica concentrate powder, 99% methanesulfonic acid and hexanoic acid is 1:0.5:0.5.

[0079] S3. The roasted product obtained in S2 is mixed with pure water at a mass ratio of 1:4, and then stirred and leached for 80 min under a water bath at a temperature of 95 ℃. After filtration, lithium-containing leachate and leaching residue are obtained.

[0080] S4. Add Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities with the precipitant and obtain the lithium-containing leachate after impurity removal.

[0081] S5. Evaporate and concentrate the lithium-containing leachate after impurity removal by 4 times, then add 130 g of sodium carbonate lithium precipitation agent to carry out lithium precipitation reaction, and filter to obtain lithium carbonate product and remaining filtrate.

[0082] Example 3

[0083] A method for efficient lithium extraction from lepidolite by low-temperature calcination of composite organic acids includes the following steps:

[0084] S1. Add 1000 g of lepidolite concentrate to a Raymond mill, then add a mixture of 200 g of activating agents sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5). Control the Raymond mill spindle speed at 120 r / min and the material moisture content at 7%. Perform pre-activation treatment in the Raymond mill for 35 min to obtain activated lepidolite concentrate powder. The mass ratio of lepidolite concentrate, sodium metabisulfite (Na2S2O5), and potassium metabisulfite (K2S2O5) is 1:0.1:0.1.

[0085] S2. The lithium mica concentrate powder obtained in S1 is mixed evenly with the composite organic acid roasting agent and placed in a high-pressure autoclave. Then, it is acidified and roasted for 120 min at a temperature of 160 ℃ and a pressure of 0.7 MPa to obtain the roasted product. The composite organic acid roasting agent includes 99% methanesulfonic acid, tartaric acid and hexanoic acid. The mass ratio of lithium mica concentrate powder, 99% methanesulfonic acid, tartaric acid and hexanoic acid is 1:0.5:0.2:0.3.

[0086] S3. The roasted product obtained in S2 is mixed with pure water at a mass ratio of 1:4, and then stirred and leached for 90 min under a water bath at a temperature of 95 ℃. After filtration, lithium-containing leachate and leaching residue are obtained.

[0087] S4. Add Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities with the precipitant and obtain the lithium-containing leachate after impurity removal.

[0088] S5. Evaporate and concentrate the lithium-containing leachate after impurity removal by 4 times, then add 135 g of sodium carbonate lithium precipitation agent to carry out lithium precipitation reaction, and filter to obtain lithium carbonate product and remaining filtrate.

[0089] Comparative Example 1

[0090] A method for efficient lithium extraction from lepidolite by low-temperature calcination of composite organic acids includes the following steps:

[0091] S1. 1000 g of lithium mica concentrate powder was mixed evenly with a composite organic acid roasting agent and placed in a high-pressure autoclave. Then, acid roasting was carried out at a temperature of 160 ℃ and a pressure of 0.7 MPa for 120 min to obtain the roasted product. The composite organic acid roasting agent included 99% methanesulfonic acid, tartaric acid and hexanoic acid. The mass ratio of lithium mica concentrate powder, 99% methanesulfonic acid, tartaric acid and hexanoic acid was 1:0.5:0.2:0.3.

[0092] S2. The roasted product obtained in S1 is mixed with pure water at a mass ratio of 1:4, and then stirred and leached for 90 min under a water bath at a temperature of 95 ℃. After filtration, lithium-containing leachate and leaching residue are obtained.

[0093] S3. Add Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities with the precipitant and obtain the lithium-containing leachate after impurity removal.

[0094] S4. Evaporate and concentrate the lithium-containing leachate after impurity removal by 4 times, then add 135 g of sodium carbonate lithium precipitation agent to carry out the lithium precipitation reaction, and filter to obtain lithium carbonate product and remaining filtrate.

[0095] Comparative Example 2

[0096] A method for efficient lithium extraction from lepidolite by low-temperature calcination of composite organic acids includes the following steps:

[0097] S1. Add 1000 g of lepidolite concentrate to a Raymond mill, then add a mixture of 200 g of activating agents sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5). Control the Raymond mill spindle speed at 120 r / min and the material moisture content at 7%. Perform pre-activation treatment in the Raymond mill for 35 min to obtain activated lepidolite concentrate powder. The mass ratio of lepidolite concentrate, sodium metabisulfite (Na2S2O5), and potassium metabisulfite (K2S2O5) is 1:0.1:0.1.

[0098] S2. The lithium mica concentrate powder obtained in S1 is mixed evenly with the organic acid roasting agent and placed in a high-pressure autoclave. Then, acid roasting is carried out at a temperature of 160 ℃ and a pressure of 0.7 MPa for 120 min to obtain the roasted product. The organic acid roasting agent is 99% methanesulfonic acid. The mass ratio of lithium mica concentrate powder to 99% methanesulfonic acid is 1:0.8.

[0099] S3. The roasted product obtained in S2 is mixed with pure water at a mass ratio of 1:5, and then stirred and leached for 90 min under a water bath at a temperature of 95 ℃. After filtration, lithium-containing leachate and leaching residue are obtained.

[0100] S4. Add Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities with the precipitant and obtain the lithium-containing leachate after impurity removal.

[0101] S5. Evaporate and concentrate the lithium-containing leachate after impurity removal by 4 times, then add 135 g of sodium carbonate lithium precipitation agent to carry out lithium precipitation reaction, and filter to obtain lithium carbonate product and remaining filtrate.

[0102] Comparative Example 3

[0103] The traditional lithium extraction process using lepidolite and sulfuric acid at high temperature includes the following steps:

[0104] S1. Mix 1000 g of lepidolite concentrate powder with 98% concentrated sulfuric acid, then place the mixture in a muffle furnace and acidify and roast it at 800 ℃ for 120 min to obtain the roasted product; wherein the mass ratio of lepidolite concentrate powder to 98% concentrated sulfuric acid is 1:0.8.

[0105] S2. The roasted product obtained in S1 is mixed with pure water at a mass ratio of 1:5, and then stirred and leached for 90 min under a water bath at a temperature of 95 ℃. After filtration, lithium-containing leachate and leaching residue are obtained.

[0106] S3. Add Ca(OH)2 to the lithium-containing leachate to adjust the pH value to above 12, so as to remove aluminum / fluorine impurities with the precipitant and obtain the lithium-containing leachate after impurity removal.

[0107] S4. Evaporate and concentrate the lithium-containing leachate after impurity removal by 4 times, then add 135 g of sodium carbonate lithium precipitation agent to carry out the lithium precipitation reaction, and filter to obtain lithium precipitate product and filtrate.

[0108] Detection and Analysis

[0109] 1) Determination of Li2O content in leaching residue, pH value of lithium-containing leachate, yield of leaching residue, and leaching rate of Li2O in lithium mica concentrate.

[0110] The formula for calculating the Li₂O leaching rate in lepidolite concentrate is: Lithium leaching rate = [Leaching liquid volume (L) × Lithium oxide concentration in leaching liquid (g / L)] / [Lithium oxide content in lepidolite concentrate (%) × Mass of lepidolite concentrate (g)] × 100%

[0111] Leaching residue yield (%) = [100% × dry weight of leaching residue (g)] / dry weight of lepidolite concentrate (g)

[0112] The results are shown in Table 1.

[0113] Table 1 shows the determination results of lithium-containing leaching solution and leaching residue.

[0114]

[0115] As can be seen from Table 1, by first activating the lithium mica concentrate with Raymond mill and activator, and then using 99% methanesulfonic acid and one or a mixture of tartaric acid and hexanoic acid as a composite organic acid roasting agent in a high pressure reactor, and then through leaching reaction, the leaching rate of Li2O can be above 95%. Comparing Example 3 and Comparative Example 1, it can be seen that when the lithium mica concentrate is pre-activated using a Raymond mill and an activator, the leaching rate of Li2O in the leachate is increased by 15.47% compared to the unactivated leachate; the yield of lithium slag is reduced by 9.48%. 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 to using 99% methanesulfonic acid alone as a roasting agent, and the yield of lithium slag is reduced by 20.11%. Comparing Example 3 and Comparative Example 3, it can be seen that when the lithium mica concentrate is pre-activated using a Raymond mill and an activator, and 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 23.3% compared to the traditional sulfuric acid 800℃ high-temperature roasting process, and the yield of lithium slag is reduced by 24.39%. This demonstrates that the novel low-temperature roasting process using composite organic acids significantly improves the leaching rate of Li2O, reduces the amount of slag, and enables the conversion of lithium in lepidolite at lower temperatures, saving energy and reducing production costs.

[0116] 2) XRD testing

[0117] The lepidolite concentrate powder pre-activated by Raymond milling and a mixed activator of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5) in S1 of Example 3, and the unactivated lepidolite concentrate powder were dried, sampled, and then subjected to XRD analysis. The results are as follows: Figure 1 As shown.

[0118] Figure 1 In the diagram, "before activation" corresponds to the unactivated lepidolite concentrate powder, while "after activation" corresponds to the lepidolite concentrate powder that has undergone pre-activation treatment using a Raymond mill and a mixed activator of sodium metabisulfite (Na2S2O5) and potassium metabisulfite (K2S2O5).

[0119] from Figure 1 Comparative analysis before and after activation revealed that the diffraction peaks of the unactivated lepidolite concentrate mostly consisted of feldspar, mica, and silica phases. After activation with the activator metabisulfite using a Raymond mill, new diffraction peaks of soluble lithium sulfate products were observed. This confirms the presence of potassium ions (K+) in the activator. + Sodium ions (Na) +) and lithium ions (Li) in lepidolite + An exchange occurred, altering the crystal structure of lepidolite. Simultaneously, during mechanical activation, the activator reacted with lepidolite in a solid-state reaction, generating soluble intermediates such as (K,Li)Al(SO4)2 and NaLiSO4. The formation of these intermediates not only contributes to the structural disruption of lepidolite but also promotes the conversion and extraction of lithium during the calcination process.

[0120] 3) Determination of leachate composition

[0121] The lithium-containing leachate obtained in S3 of Example 3 and the lithium-containing leachate obtained in S2 of Comparative Example 3 were analyzed by inductively coupled plasma atomic emission spectrometry (ICP), gas chromatography-mass spectrometry (GC-MS), atomic absorption spectrophotometry (AAS), and automatic potentiometric titration, respectively. The results are shown in Tables 2 and 3.

[0122] Table 2 shows the main components of the lithium-containing leachate obtained in Example 3.

[0123]

[0124] Note: The organic acid anion is methanesulfonate ion CH3SO3 － tartrate ion C4H4O6 2- and hexanoate ion C6H 13 COO − .

[0125] Table 3 shows the main components of the lithium-containing leachate obtained in Comparative Example 3.

[0126]

[0127] Table 2 shows that the Li concentration in the leachate after calcination was 7.85 g / L. The main impurities included Ca, Al, Fe, SiO2, and F, with other impurities including Mg and Mn. Compared to the traditional sulfuric acid method (Table 3), the contents of Ca, Fe, and F were below 0.1 g / L, the Al content decreased by 31.2%, and the SiO2 content decreased by 59.4%. The contents of other impurity elements were below 0.01 g / L. This fully demonstrates that the mild reaction of the organic acid reduced the dissolution of impurity elements, thus largely ensuring the purity of the subsequent product.

[0128] In summary, the method for high-efficiency lithium extraction from lepidolite by low-temperature roasting with composite organic acids of the present invention effectively improves the surface properties of lepidolite by adding an activator to the lepidolite concentrate for pre-activation treatment, making it more sensitive to the subsequent acid roasting process, thereby improving the lithium extraction efficiency. During the acid roasting process, the organic acid components such as methanesulfonic acid in the composite organic acid roasting agent can chemically react with the silicate structure in 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 organic acids can also reduce the bond energy of Si-O bonds, allowing them to dissociate at lower temperatures, thereby releasing lithium ions locked in the crystal 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 lepidolite and the difficulty in dissociating high bond energy Si-O bonds in traditional methods, but also reduces energy consumption and increases the lithium leaching rate through low-temperature roasting, which has significant economic benefits and environmental friendliness, providing a new technical approach for the efficient utilization of lepidolite resources. Compared to the sulfuric acid process alone, this method effectively improves the lithium conversion rate in lepidolite while reducing the roasting temperature and saving energy. Furthermore, although the sulfuric acid process alone is highly adaptable to different raw materials, it generates a large amount of waste residue. The synergistic effect of the activator and the composite organic acid effectively reduces the amount of residue and environmental pollution, which is of great significance to the sustainable development of the lithium industry and has significant application value in the field of ore-based lithium extraction technology.

[0129] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for efficiently extracting lithium from low-temperature calcined lepidolite with composite organic acid, characterized in that, The method comprises the following steps: S1, adding an activator to the lithium mica concentrate, pre-activating treatment, to obtain an activated lithium mica concentrate powder; S2, mixing the lithium mica concentrate powder with a composite organic acid roasting agent for acidizing roasting, to obtain a roasting product; S3, adding water to the roasting product for leaching, to obtain a lithium-containing leaching solution; The composite organic acid roasting agent at least comprises methyl sulfonic acid; The activator is selected from one or both of sodium pyrosulfite and potassium pyrosulfite; The composite organic acid roasting agent further comprises one or both of tartaric acid and hexanoic acid.

2. The method for efficient lithium extraction from low-temperature calcined lepidolite with composite organic acid according to claim 1, characterized in that, The pre-activating treatment is to add the lithium mica concentrate to a Raymond mill, add the activator, control the rotation speed of the Raymond mill main shaft to be 60-120 r / min, the water content of the material to be 5-10 %, and the pre-activating treatment time of the Raymond mill to be 30-40 min, to realize the pre-activation of the lithium mica concentrate.

3. The method for efficient lithium extraction from low-temperature calcined lepidolite with composite organic acid according to claim 1, characterized in that, The activator is selected from sodium pyrosulfite and potassium pyrosulfite; The mass ratio of the lithium mica concentrate, sodium pyrosulfite and potassium pyrosulfite is 1:0.1-0.3:0.1-0.

2.

4. The method for efficient lithium extraction from lepidolite by low-temperature calcination with composite organic acid according to claim 1, characterized in that, The composite organic acid roasting agent comprises methyl sulfonic acid, tartaric acid and hexanoic acid; The mass ratio of the lithium mica concentrate powder, methyl sulfonic acid, tartaric acid and hexanoic acid is 1:0.5-0.8:0.2-0.4:0.3-0.

5.

5. The method for efficient lithium extraction from lepidolite by low-temperature calcination with composite organic acid according to claim 1, characterized in that, The acidizing roasting is performed in an autoclave, the temperature of the acidizing roasting is 100-300 ℃, the pressure of the acidizing roasting is 0.3-0.7 MPa, and the time of the acidizing roasting is 60-120 min; And / or, the temperature of the leaching is 90-99 ℃, and the time of the leaching is 60-90 min; And / or, the mass ratio of the roasting product to water is 1:3-5.

6. The method for efficient lithium extraction from lepidolite by low-temperature calcination with composite organic acid according to claim 1, characterized in that, The chemical composition and mass percentage of the lithium mica 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 / %, and the rest is other impurities.

7. The method for high efficient lithium extraction from low temperature calcined lepidolite with composite organic acid according to any one of claims 1 to 6, characterized in that, Further comprising: S4, removing aluminum and fluorine impurities from the lithium-containing leaching solution by a precipitant, to obtain a lithium-containing leaching solution after impurity removal; S5, evaporating and concentrating the lithium-containing leaching solution after impurity removal, then adding a lithium precipitation agent for normal-temperature and normal-pressure lithium precipitation reaction, and filtering, to obtain a lithium precipitate product and a remaining filtrate.

8. The method for efficient lithium extraction from lepidolite by composite organic acid low-temperature calcination according to claim 7, 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 precipitation agent is selected from a carbonate.

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