Process for the preparation of lithium carbonate from lithium ores

Abstract

The application provides a method for preparing lithium carbonate from lithium ore, and belongs to the field of metal smelting, wherein lithium clay and lepidolite flotation concentrate are mixed to obtain lithium ore mixture; the lithium ore mixture is mixed with acid liquor to obtain first material; the first material is sequentially subjected to first roasting and second roasting to obtain second material; the second material is subjected to grinding treatment, and then a leaching agent is added for leaching; after filtration, a lithium-containing leaching liquor is obtained; the lithium-containing leaching liquor is sequentially subjected to iron removal, aluminum removal by extraction and impurity removal treatment to obtain purified liquor; the purified liquor is subjected to lithium extraction enrichment, and then subjected to back extraction to obtain lithium-rich solution; the lithium-rich solution is reacted with sodium carbonate to obtain lithium carbonate. The lepidolite and lithium clay are mixed, and a two-stage roasting process is adopted, so that the leaching of aluminum ions is effectively inhibited; in combination with the high-temperature aluminum solidification and low-acid leaching process, the concentration of aluminum ions in the solution is reduced, and the loss of lithium is reduced, so that the method is an efficient lithium extraction method.

Description

Technical Field

[0001] This invention relates to the field of metal smelting technology, and specifically to a method for preparing lithium carbonate from lithium ore. Background Technology

[0002] Lithium, as the lightest metallic element, possesses physical properties such as a silvery-white appearance, soft texture, and low density. It is chemically extremely reactive, exhibiting significant electrochemical activity, and readily forms alloys or compounds with other elements. Therefore, it is widely used in numerous industrial fields, especially in battery materials. Among my country's various lithium resources, lepidolite is concentrated in Jiangxi Province; clay-type lithium deposits are widely distributed and have relatively good mining conditions, particularly concentrated in the southwestern Sichuan, Yunnan, and Guizhou regions. For example, clay-type lithium deposits are commonly found in Guizhou, often associated with bauxite and coal mines.

[0003] In recent years, the process of smelting lepidolite to produce lithium carbonate has evolved from the early acid process to the salt roasting-leaching process. The acid process, due to severe equipment corrosion and difficulty in handling aluminum impurities, has gradually been replaced by the salt roasting process. However, with the continuous expansion of mining scale, the lithium carbonate industry faces new challenges such as excessive slag volume and low comprehensive utilization rate of lepidolite. Currently, lithium extraction processes from clay-type lithium ores mainly include three types: roasting-leaching with additives, direct roasting-leaching, and field-enhanced leaching. Existing roasting-leaching processes generally suffer from the problem of simultaneous dissolution of lithium and aluminum during leaching, resulting in generally low lithium concentrations in the leachate (typically 200~700 mg / L) and high aluminum content (up to 15 g / L). If conventional methods of adjusting pH to form hydroxide precipitates are used to remove aluminum, the lithium loss rate due to entrainment and adsorption can reach as high as 50%. Therefore, effectively suppressing aluminum dissolution during roasting-leaching while ensuring a high lithium recovery rate has become a key aspect of optimizing this process.

[0004] In view of this, it is necessary to design a method for preparing lithium carbonate from lithium ore to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a method for preparing lithium carbonate from lithium ore, aiming to solve the technical problem that lithium and aluminum are dissolved simultaneously in the existing leaching process, resulting in an excessively high lithium loss rate in the subsequent aluminum removal process.

[0006] This application provides a method for preparing lithium carbonate from lithium ore, comprising the following steps:

[0007] S1. Lithium clay is mixed with lepidolite flotation concentrate to obtain lithium ore mixture, and the lithium ore mixture is mixed with acid to obtain the first material;

[0008] S2. The first material is subjected to a first roasting and a second roasting in sequence to obtain the second material;

[0009] S3. Grind the second material, then add a leaching agent for leaching, and filter to obtain a lithium-containing leachate;

[0010] S4. The lithium-containing leachate is subjected to iron removal, aluminum extraction, and impurity removal treatments in sequence to obtain a purified solution;

[0011] S5. Extract and enrich lithium in the purified liquid, and then back-extract to obtain a lithium-rich solution.

[0012] S6. React the lithium-rich solution with sodium carbonate to obtain lithium carbonate.

[0013] As a further improvement of this application, in step S1, the mass ratio of lithium clay to lithium mica flotation concentrate is (0.2~0.7):1; the mass ratio of lithium ore mixture to acid solution is 1:(0.6~0.8); and the acid solution is concentrated sulfuric acid with a concentration of 96~98wt%.

[0014] As a further improvement of this application, in step S2, the temperature of the first roasting is 340~380°C and the roasting time is 20~30min; the temperature of the second roasting is 820~850°C and the roasting time is 20~30min.

[0015] As a further improvement of this application, in step S3, the proportion of particles with a particle size of -74μm after grinding is 75~85wt%.

[0016] As a further improvement of this application, the leaching agent is a dilute sulfuric acid solution with a concentration of 0.001~0.003mol / L; the mass ratio of the ground material to the leaching agent is 1:(1~2), and the leaching time is 30~40min.

[0017] As a further improvement of this application, in step S4, the aluminum extraction is carried out using an organic phase containing di(2-ethylhexyl) phosphate at a pH of 2.5 to 3.5.

[0018] As a further improvement of this application, the iron removal is carried out under conditions of pH 3.5 to 4.5; the impurity removal is carried out under conditions of pH 11 to 12.

[0019] As a further improvement of this application, in step S5, the extraction and enrichment of lithium is carried out using an organic phase containing a β-diketone main extractant and a phosphine oxide co-extractant, under conditions where the pH value is not lower than 12.5.

[0020] As a further improvement of this application, the back-extraction uses sulfuric acid with a concentration of 1~3 mol / L as the back-extraction agent.

[0021] As a further improvement to this application, the raffinate produced in step S5 is further concentrated and evaporated to obtain sodium sulfate by-product.

[0022] The beneficial effects of this application are as follows:

[0023] This application provides a method for preparing lithium carbonate from lithium ore. The method involves mixing lithium clay with lepidolite flotation concentrate to obtain a lithium ore mixture. This mixture is then mixed with acid to obtain a first material. The first material is subsequently subjected to a first roasting and a second roasting to obtain a second material. The second material is then ground, followed by leaching with a leaching agent. After filtration, a lithium-containing leachate is obtained. This leachate is then subjected to iron removal, aluminum extraction, and impurity removal to obtain a purified solution. The purified solution is then extracted to enrich lithium, followed by back-extraction to obtain a lithium-rich solution. The lithium-rich solution is then reacted with sodium carbonate to obtain lithium carbonate. This application effectively suppresses aluminum ion leaching by mixing lepidolite and lithium clay and employing a two-stage roasting process, solving the problem of aluminum immobilization during the roasting of single-stage lithium clay. In the second-stage roasting, a fluidized bed is innovatively used instead of a traditional rotary kiln, fundamentally avoiding kiln clogging and ensuring continuous and stable operation of the roasting process. By combining high-temperature aluminum fixation with low-acid leaching, this process significantly inhibits aluminum dissolution while promoting efficient lithium-ion dissolution, thus reducing the difficulty of subsequent aluminum-ion separation. The leaching solution, after extraction under acidic conditions, can reduce the aluminum content to below 100 ppm, effectively preventing impurities from affecting the quality of battery-grade lithium carbonate products. Furthermore, this process generates 30% less slag than the traditional salt method, making it more environmentally friendly.

[0024] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0026] Figure 1 This is a flowchart of a method for preparing lithium carbonate from lithium ore provided in Example 1 of this application;

[0027] Figure 2This is the XRD pattern of the leaching residue in Example 1 of this application;

[0028] Figure 3 This is an MLA diagram of the leaching residue in Example 1 of this application. Detailed Implementation

[0029] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0033] Existing roasting-leaching processes commonly suffer from the problem of simultaneous leaching of lithium and aluminum during the leaching of clay-type lithium ores, resulting in generally low lithium concentrations and high aluminum content in the leachate. If conventional methods such as adjusting pH to form hydroxide precipitates are used to remove aluminum, the lithium loss rate due to entrainment and adsorption can be as high as 50%.

[0034] To address the technical problem of simultaneous lithium and aluminum leaching in existing roasting-leaching processes, leading to excessively high lithium loss rates in subsequent aluminum removal processes, this application provides a method for preparing lithium carbonate from lithium ore. This method involves preparing lithium carbonate by a mixture of lepidolite and lithium clay through a two-stage roasting-leaching-aluminum removal-impurity removal-lithium precipitation-extraction-concentration crystallization process. This approach effectively inhibits aluminum dissolution, reduces the difficulty of subsequent aluminum ion separation, and improves lithium recovery rates.

[0035] This application provides a method for preparing lithium carbonate from lithium ore, including the following steps:

[0036] S1. Lithium clay is mixed with lepidolite flotation concentrate to obtain lithium ore mixture. The lithium ore mixture is then mixed with acid to obtain the first material.

[0037] S2. The first material is subjected to a first roasting and a second roasting in sequence to obtain the second material;

[0038] S3. Grind the second material, then add a leaching agent for leaching, and filter to obtain a lithium-containing leachate;

[0039] S4. The lithium-containing leachate is subjected to iron removal, aluminum extraction and impurity removal treatments in sequence to obtain a purified solution;

[0040] S5. Extract and enrich lithium in the purified liquid, and then back-extract to obtain a lithium-rich solution.

[0041] S6. React the lithium-rich solution with sodium carbonate to obtain lithium carbonate.

[0042] In the technical solution of this application embodiment, lithium clay and lepidolite concentrate are mixed, and staged roasting combined with acid synergy is employed. Utilizing the complementary effect of the two ores' components, impurities such as aluminum are effectively solidified during roasting, thereby inhibiting their dissolution in subsequent leaching at the source. This method significantly reduces the aluminum content in the leachate, avoiding the high lithium loss rate caused by precipitation in traditional aluminum removal processes. Combined with subsequent extraction, purification, and enrichment technologies, high-purity lithium carbonate is ultimately obtained while ensuring a high lithium recovery rate, effectively solving the problems of low lithium recovery rate and high impurity removal costs in existing technologies.

[0043] Furthermore, in some embodiments, in step S1, the mass ratio of lithium clay to lepidolite flotation concentrate is (0.2~0.7):1; the mass ratio of lithium ore mixture to acid is 1:(0.6~0.8); and the acid is concentrated sulfuric acid with a concentration of 96~98wt%.

[0044] In the technical solution of this application embodiment, by limiting the mass ratio of lithium clay to lepidolite concentrate and using a specific proportion of high-concentration sulfuric acid for mixing, the chemical composition and reactivity of the mixture are precisely controlled. Specific components in the lithium clay (such as aluminosilicates) preferentially form stable sulfates (such as aluminum sulfate) that are insoluble in subsequent leaching agents during the high-temperature reaction of concentrated sulfuric acid, thereby locking in most aluminum impurities before roasting. This pre-curing synergistic effect further enhances the inhibition of aluminum leaching during roasting, ensuring that the leachate has a lower aluminum content and a higher lithium-aluminum ratio. This creates extremely favorable conditions for subsequent efficient and low-loss extraction to remove aluminum, fundamentally improving the overall lithium recovery rate of the entire process. Specifically, the lithium clay particles with a size of -200 μm account for 75-85%, and the lepidolite flotation concentrate particles with a size of -106 μm account for 75-85%; the water content of both the lithium clay and the lepidolite flotation concentrate does not exceed 10%.

[0045] Furthermore, in some embodiments, in step S2, the temperature of the first roasting is 340~380°C and the roasting time is 20~30 min; the temperature of the second roasting is 820~850°C and the roasting time is 20~30 min.

[0046] In the technical solution of this application embodiment, the structural transformation and chemical activation of materials are achieved stepwise by precisely controlling the temperature gradient. The first low-temperature roasting uses concentrated sulfuric acid to pre-sulfatate the mixed ore, converting valuable elements such as lithium into soluble sulfates. The second high-temperature roasting further disrupts the ore's crystal structure, fully activating the lithium sulfate and ensuring that impurity phases (such as aluminum sulfate) are sintered and solidified, transforming into glassy or leucite, reducing their activity in water. This synergistic mechanism of "low-temperature activation and high-temperature solidification" maximizes the subsequent lithium leaching rate while fundamentally inhibiting aluminum dissolution, contributing to the subsequent acquisition of a lithium-containing leachate with low impurity content and excellent quality. Specifically, the first roasting equipment is preferably a rotary kiln, and the second roasting equipment is preferably a fluidized bed. The material obtained from the first roasting is crushed and ground until the proportion of particles with a particle size of -106μm is 75-85%, and then subjected to the second roasting. The sulfur-containing flue gas generated during the roasting process is absorbed by calcium hydroxide. The resulting solid is filtered and dried using the residual heat of the flue gas, and then added to the material obtained from the first roasting, which is beneficial for the second roasting to solidify aluminum.

[0047] Furthermore, in some embodiments, in step S3, the proportion of particles with a particle size of -74μm after grinding is 75~85wt%.

[0048] In the technical solution of this application embodiment, precise control of grinding particle size helps to achieve the optimal balance between leaching reaction kinetics and solid-liquid separation efficiency. This particle size range provides a sufficiently large specific surface area to ensure that the active lithium component in the roasted material is in full contact with the leaching agent, thereby achieving rapid and efficient leaching; at the same time, it avoids excessive fine particles generated due to over-grinding. These fine particles can easily lead to increased slurry viscosity, filtration difficulties, and may increase the physical entrainment and dissolution of impurity elements. While ensuring a high lithium leaching rate, it significantly improves subsequent filtration performance, reduces the energy consumption and difficulty of solid-liquid separation, and helps to obtain a cleaner leachate.

[0049] Furthermore, in some embodiments, the leaching agent is a dilute sulfuric acid solution with a concentration of 0.001~0.003 mol / L; the mass ratio of the ground material to the leaching agent is 1:(1~2), and the leaching time is 30~40 min.

[0050] In the technical solution of this application embodiment, after the aforementioned roasting treatment, lithium is converted into sulfate, which is highly soluble in water, while impurities such as aluminum are solidified into stable compounds with extremely low solubility in a weakly acidic environment. Therefore, even extremely low concentrations of dilute sulfuric acid are sufficient to efficiently dissolve active lithium, while simultaneously strongly inhibiting the dissolution of solidified aluminum impurities. This method achieves a high lithium leaching rate while maximally maintaining impurities such as aluminum in the solid phase, ensuring high purity (low aluminum content) of the leachate from the source. This not only significantly reduces the load and cost of subsequent aluminum removal processes but also effectively avoids the risk of equipment corrosion and secondary dissolution of impurities due to excessively high acidity, achieving a highly efficient, economical, and environmentally friendly leaching process.

[0051] Furthermore, in some embodiments, in step S4, the aluminum removal extraction is carried out using an organic phase containing di(2-ethylhexyl) phosphate at a pH of 2.5 to 3.5.

[0052] In the technical solution of this application embodiment, aluminum is removed by extraction using an organic phase containing di(2-ethylhexyl) phosphate (D2EHPA) at a specific pH value. D2EHPA has a highly efficient and selective chelating ability for trivalent aluminum ions. Within this pH range, aluminum ions are mainly in the form of Al. 3+Lithium ions exist in their aqueous form and can be effectively extracted into the organic phase by D2EHPA. However, due to their low charge and small radius, lithium ions have a weak binding ability with the extractant and are mostly retained in the aqueous phase. This highly efficient solvent extraction method achieves deep separation of lithium and aluminum. Compared with traditional precipitation methods, it fundamentally avoids lithium loss caused by entrainment due to aluminum hydroxide co-precipitation, significantly improving the lithium recovery rate. Simultaneously, the purified solution obtained has higher purity, ensuring the subsequent preparation of high-quality lithium carbonate. Specifically, the organic phase is a sulfonated kerosene solution of D2EHPA, and the raffinate undergoes subsequent impurity removal treatment. The intermediate product obtained from extraction is washed with pure water or dilute sulfuric acid and then back-extracted with 1-2 mol / L sulfuric acid.

[0053] Furthermore, in some embodiments, iron removal is carried out at a pH of 3.5 to 4.5; impurity removal is carried out at a pH of 11 to 12.

[0054] In the technical solution of this application embodiment, under the condition of pH value 3.5~4.5, iron ions (Fe) 3+ The process preferentially hydrolyzes to form ferric hydroxide precipitate, while lithium ions and most other divalent metal ions remain stable in the solution, thus achieving selective removal of iron. Under strongly alkaline conditions with a pH of 11-12, residual divalent impurity ions such as calcium and magnesium in the solution form hydroxide precipitates, while lithium ions remain in the liquid phase due to the high solubility of lithium hydroxide. Through this stepwise and precise pH control, targeted and efficient removal of iron and other impurity ions is achieved with minimal lithium loss, further purifying the solution beyond aluminum extraction and ensuring extremely high purity of the solution entering the subsequent lithium enrichment process. Specifically, sodium hydroxide is added to the lithium-containing leachate to adjust the pH to 3.5-4.5 for iron removal; sodium hydroxide and calcium oxide are added to the raffinate obtained from aluminum extraction to adjust the pH to 11-12 for fluoride, calcium, and magnesium removal.

[0055] Furthermore, in some embodiments, in step S5, the extraction and enrichment of lithium is carried out using an organic phase comprising a β-diketone primary extractant and a phosphine oxide co-extractant, under conditions where the pH value is not lower than 12.5.

[0056] In the technical solution of this application embodiment, at this pH, lithium ions mainly exist in a free state. β-diketone extractants capture lithium ions through chelation, while phosphine oxide co-extractants coordinate with lithium ions through oxygen atoms to form a more stable and lipophilic ternary complex, thereby greatly enhancing the ability of lithium to transfer from the aqueous phase to the organic phase. This co-extraction system can efficiently and selectively enrich lithium from purification solutions with relatively low lithium concentrations. Compared with single extractants, it has advantages such as large extraction capacity, fast phase separation, and high selectivity for other alkali metal / alkaline earth metal ions, achieving efficient concentration and purification of lithium, and significantly reducing reagent consumption and costs in back-extraction and subsequent precipitation processes. Specifically, the main extractant is β-diketone and its derivatives, the co-extractant is a compound containing a phosphine oxide group, and the diluent is sulfonated kerosene.

[0057] Furthermore, in some embodiments, sulfuric acid with a concentration of 1-3 mol / L is used as the back-extraction agent.

[0058] In the technical solution of this application embodiment, the competitive binding ability of high-concentration hydrogen ions with β-diketones and phosphine oxide extractants in the organic phase is much stronger than that of lithium ions. This allows for the rapid displacement of lithium ions from the organic complex, returning them to the aqueous phase as lithium sulfate, while the extractant reverts to its free form and is regenerated and recycled. This method can efficiently and rapidly back-extract almost completely lithium loaded in the organic phase, obtaining a high-concentration, high-purity lithium-rich sulfate solution. Simultaneously, it achieves low-cost regeneration and recycling of expensive extractants, significantly reducing the overall operating cost of the process and ensuring the purity and yield of the final lithium carbonate product.

[0059] Furthermore, in some embodiments, the raffinate produced in step S5 is further concentrated and evaporated to obtain sodium sulfate by-product.

[0060] In the technical solution of this application embodiment, the raffinate is the aqueous phase after lithium extraction and enrichment, which still contains unextracted alkali metal sulfates such as sodium and potassium, as well as a small amount of other soluble salts. Through concentration and evaporation, these salts can crystallize out of the solution, not only achieving wastewater reduction and near-zero discharge, meeting the requirements of green and environmentally friendly production, but more importantly, transforming the potentially wasteful raffinate into a commercially valuable byproduct of sodium sulfate, opening up a new profit growth point, thereby significantly improving the economic benefits and resource utilization rate of the entire lithium ore comprehensive utilization process. Specifically, before evaporation and concentration, the raffinate needs to undergo activated carbon adsorption and resin degreasing to reduce the organic matter content in the solution.

[0061] Furthermore, in step S6, the sodium carbonate is a saturated sodium carbonate solution with a concentration of 290~310 g / L. The lithium precipitation mother liquor obtained after the reaction of the lithium-rich solution with sodium carbonate is mixed with the purified solution and used as the raw material for lithium extraction and enrichment.

[0062] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0063] Example 1

[0064] This embodiment provides a method for preparing lithium carbonate from lithium ore. The chemical compositions of the lepidolite and lithium clay used are shown in Table 1.

[0065] Table 1 Chemical composition of lithium ore

[0066]

[0067] like Figure 1 As shown, the specific steps include:

[0068] S1. Mix lepidolite flotation concentrate, lithium clay, 98% sulfuric acid and water in a mass ratio of 80:20:70:17 to obtain the first material;

[0069] S2. The first material is first roasted in a rotary kiln for 30 minutes at a temperature of 350°C and a rotation speed of 0.7 r / min. After roasting, the material is crushed and ground to a particle size of -106 μm, accounting for 80%. Then, it is fed to a fluidized bed for a second roasting at a gas velocity of 28 cm / sec and a temperature of 830°C. The material stays in the fluidized bed for about 23 minutes to obtain the second material. The second material contains 1.69% soluble lithium, 1.88% total lithium, and a conversion rate of 89.9%.

[0070] S3. The second material is ground to a particle size of -74μm (80wt%), then mixed with 0.002mol / L sulfuric acid at a mass ratio of 1:2 and leached for 40 minutes. After filtration, a lithium-containing leachate is obtained; the lithium ion leaching rate is 98%; the aluminum ion leaching rate is 15%; and the rubidium ion leaching rate is 52%. Figures 2 to 3 As shown, the phase analysis of the leaching residue indicates that the aluminosilicates are mainly contained in leucite. Due to the dense crystal structure of leucite, the aluminum in it is chemically stable and difficult to leach. In addition, gypsum, quartz and feldspar are also present in the residue.

[0071] S4. Add sodium hydroxide to the lithium-containing leachate to adjust the pH of the solution to 4, filter to remove iron, adjust the pH of the filtrate to 3, add a sulfonated kerosene solution of D2EHPA and perform a three-stage countercurrent extraction to remove aluminum. The volume ratio of D2EHPA to kerosene is 1:10. After washing the organic phase once with dilute sulfuric acid, back-extract with 2 mol / L sulfuric acid to recover alumina. The aluminum ion concentration in the raffinate decreases from 1.03 g / L to 0.015 g / L. Add sodium hydroxide and calcium oxide to the raffinate to adjust the pH to 11, generate a precipitate, filter, and obtain the filtrate. Pass the filtrate through an aminophosphate chelating resin to remove divalent metal ions to obtain a purified solution. The purified solution contains 10 g / L lithium oxide, 17 g / L sodium ions, 16 g / L potassium ions, and 35 ppm fluoride ions.

[0072] S5. Extract and enrich lithium from the purified solution using LIX as the extractant. ® The mixture was prepared by mixing 54 (1-phenyldecane-1,3-dione β-diketone chelating extractant), TBP (tributyl phosphate), and sulfonated kerosene in a volume ratio of 21:9:70. During the extraction stage, the pH of the aqueous phase was controlled to be no lower than 12.5, and the mixture was stirred for 4 minutes at a 1:1 ratio (O / A). After three stages of countercurrent extraction, the lithium extraction rate reached 99%. The loaded organic phase was washed with pure water to remove entrained impurities. In the back-extraction stage, 2 mol / L sulfuric acid was used as the back-extraction agent at a 4.5:1 ratio (O / A) to obtain a lithium-rich solution with a back-extraction rate of 99%. The resulting back-extraction solution contained approximately 45 g / L of lithium oxide. The raffinate produced during the extraction process was evaporated and concentrated to produce sodium sulfate (anhydrous sodium sulfate), which can be sold as a byproduct.

[0073] S6. The lithium-rich solution is mixed with 300 g / L saturated sodium carbonate solution at 95°C to precipitate lithium, resulting in lithium carbonate and lithium precipitation mother liquor. After multiple stirring and washing, the lithium carbonate meets the requirements for battery-grade lithium carbonate. The lithium oxide concentration in the lithium precipitation mother liquor is 5.12 g / L. It is returned to step S5 and mixed with the purification solution as a raw material for lithium extraction and enrichment.

[0074] Example 2

[0075] This embodiment provides a method for preparing lithium carbonate from lithium ore. The chemical compositions of the lepidolite and lithium clay used are shown in Table 1. The method specifically includes the following steps:

[0076] S1. Mix lepidolite flotation concentrate, lithium clay, 98% sulfuric acid and water in a mass ratio of 60:40:70:17 to obtain the first material;

[0077] S2. The first material is first roasted in a rotary kiln for 30 minutes at 350°C and 0.7 r / min. After roasting, the material is crushed and ground to a particle size of -106 μm, accounting for 80%. Then, it is fed to a fluidized bed for a second roasting. The bulk material enters from above the fluidized bed and exits from the side and below; air enters from below the fluidized bed and exits from the side and above, entering the tail gas collection and treatment device. The air velocity suspends the ore in the fluidized bed. The material thickness in the fluidized bed is 1.5 times the compacted material thickness, the gas velocity is 28 cm / sec, the temperature is 830°C, and the material stays in the fluidized bed for about 23 minutes to obtain the second material. The second material contains 1.45% soluble lithium, 1.72% total lithium, and a conversion rate of 84.3%. The gas generated during roasting can be desulfurized, defluorinated, and denitrified by the tail gas absorption device to meet the emission standards.

[0078] S3. The second material is ground to a particle size of -74μm (80wt%), then mixed with 0.002mol / L sulfuric acid at a mass ratio of 1:2 and stirred for 40 minutes. After filtration, a lithium-containing leachate is obtained; the lithium ion leaching rate is 96%; the aluminum ion leaching rate is 23%; and the rubidium ion leaching rate is 47%.

[0079] S4. Add sodium hydroxide to the lithium-containing leachate to adjust the pH of the solution to 4, filter to remove iron, adjust the pH of the filtrate to 3, add a sulfonated kerosene solution of D2EHPA and perform a three-stage countercurrent extraction to remove aluminum. The volume ratio of D2EHPA to kerosene is 1:10. After washing the organic phase once with dilute sulfuric acid, back-extract with 2 mol / L sulfuric acid. The aluminum ion concentration in the raffinate decreases from 1.92 g / L to 0.0154 g / L. Add sodium hydroxide and calcium oxide to the raffinate to adjust the pH to 11, generate a precipitate, filter, and obtain the filtrate. Pass the filtrate through an aminophosphate chelating resin to remove divalent metal ions to obtain a purified solution. The purified solution contains 9 g / L lithium oxide, 16 g / L sodium ions, 14 g / L potassium ions, and 34 ppm fluoride ions.

[0080] S5. Extract and enrich lithium from the purified solution using LIX as the extractant. ® 54. TBP and sulfonated kerosene were prepared at a volume ratio of 21:9:70. During the extraction stage, the pH of the aqueous phase was controlled to be no less than 12.5, and the mixture was stirred for 4 minutes at a 1:1 ratio (O / A). After three stages of countercurrent extraction, the lithium extraction rate reached 99%. The loaded organic phase was washed with pure water to remove impurities. In the back-extraction stage, 2 mol / L sulfuric acid was used as the back-extraction agent at a 4.5:1 ratio (O / A) to obtain a lithium-rich solution with a back-extraction rate of 99%. The resulting back-extraction solution contained approximately 41 g / L of lithium oxide. The raffinate produced during the extraction process was evaporated and concentrated to produce sodium sulfate (anhydrous sodium sulfate), which can be sold as a byproduct.

[0081] S6. The lithium-rich solution is mixed with 300 g / L saturated sodium carbonate solution at 95°C to precipitate lithium, resulting in lithium carbonate and lithium precipitation mother liquor. After multiple stirring and washing, the lithium carbonate meets the requirements for battery-grade lithium carbonate. The lithium oxide concentration in the lithium precipitation mother liquor is 5.01 g / L. It is returned to step S5 and mixed with the purification solution as a raw material for lithium extraction and enrichment.

[0082] Comparative Example 1

[0083] Comparative Example 1 provides a method for preparing lithium carbonate from lithium ore. The chemical compositions of the lepidolite and lithium clay used are shown in Table 1. The method specifically includes the following steps:

[0084] S1. Lithium clay, 98% sulfuric acid, and water are mixed in a mass ratio of 100:70:17 to obtain the first material;

[0085] S2. The first material is roasted in a rotary kiln for 30 minutes at a temperature of 850°C and a rotation speed of 0.7 r / min to obtain the second material; the second material contains 1.008% soluble lithium, 1.12% total lithium, and a conversion rate of 90.0%, and the rotary kiln is sealed.

[0086] S3. The second material is ground to a particle size of -74μm (80wt%), then mixed with 0.002mol / L sulfuric acid at a mass ratio of 1:2 and stirred for 40 minutes. After filtration, a lithium-containing leachate is obtained; the lithium ion leaching rate is 96%; and the aluminum ion leaching rate is 70%.

[0087] S4. Add sodium hydroxide to the lithium-containing leachate to adjust the pH of the solution to 4, filter to remove iron, adjust the pH of the filtrate to 3, add a sulfonated kerosene solution of D2EHPA and perform a three-stage countercurrent extraction to remove aluminum. The volume ratio of D2EHPA to kerosene is 1:10. After washing the organic phase once with dilute sulfuric acid, back-extract with 2 mol / L sulfuric acid. The aluminum ion concentration in the raffinate decreases from 15 g / L to 0.02 g / L, which easily forms a three-phase system. Add sodium hydroxide and calcium oxide to the raffinate to adjust the pH to 11, generate a precipitate, filter, and obtain the filtrate. Pass the filtrate through an aminophosphate chelating resin to remove divalent metal ions to obtain a purified solution containing 7 g / L of lithium oxide.

[0088] S5. Extract and enrich lithium from the purified solution using LIX as the extractant. ®54. TBP and sulfonated kerosene were prepared at a volume ratio of 21:9:70. During the extraction stage, the pH of the aqueous phase was controlled to be no lower than 12.5, and the mixture was stirred for 4 minutes at a 1:1 ratio (O / A). After three stages of countercurrent extraction, the lithium extraction rate reached 99%. The loaded organic phase was washed with pure water to remove entrained impurities. In the back-extraction stage, 2 mol / L sulfuric acid was used as the back-extraction agent at a 6:1 ratio (O / A), and the back-extraction rate reached 99%. The resulting back-extraction solution contained approximately 42 g / L of lithium oxide. The raffinate produced during the extraction process was evaporated and concentrated to produce sodium sulfate (anhydrous sodium sulfate), which can be sold as a byproduct.

[0089] S6. The lithium-rich solution is mixed with 300 g / L saturated sodium carbonate solution at 95°C to precipitate lithium, resulting in lithium carbonate and lithium precipitation mother liquor. After multiple stirring and washing, the lithium carbonate meets the requirements for battery-grade lithium carbonate. The lithium oxide concentration in the lithium precipitation mother liquor is 5.52 g / L, and it is returned to step S5 to be mixed with the purification solution as a raw material for lithium extraction and enrichment.

[0090] As can be seen from Examples 1-2, the method for preparing lithium carbonate from lithium ore provided in this application is less prone to kiln clogging during roasting, has a low aluminum ion concentration in the leachate, and a good removal effect, which reduces the generation of three phases in the subsequent aluminum removal process and reduces production costs. In Comparative Example 1 and Example 1, with the same conversion rate, the aluminum leaching rate after roasting is significantly higher, indicating that the two-stage roasting process adopted in this application effectively inhibits the leaching of aluminum ions.

[0091] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for producing lithium carbonate from a lithium ore, characterized by, The method comprises the following steps: S1. mixing lithium clay with lithium mica flotation concentrate to obtain lithium ore mixture, and mixing the lithium ore mixture with acid liquor to obtain first material; The mass ratio of the lithium clay to the lithium mica flotation concentrate is (0.2-0.7):1; the mass ratio of the lithium ore mixture to the acid liquor is 1:(0.6-0.8); the acid liquor is concentrated sulfuric acid with a concentration of 96-98 wt%; S2. sequentially performing first roasting and second roasting on the first material to obtain second material; The temperature of the first roasting is 340-380°C, and the roasting time is 20-30 min; the temperature of the second roasting is 820-850°C, and the roasting time is 20-30 min; S3. performing grinding treatment on the second material, then adding leaching agent for leaching, and filtering to obtain lithium-containing leaching liquor; The leaching agent is dilute sulfuric acid solution with a concentration of 0.001-0.003 mol / L; S4. sequentially performing iron removal, aluminum removal by extraction, and fluorine, calcium, and magnesium removal on the lithium-containing leaching liquor to obtain purified liquor; S5. performing lithium enrichment by extraction on the purified liquor, and then performing back extraction to obtain lithium-rich solution; S6. reacting the lithium-rich solution with sodium carbonate to obtain lithium carbonate.

2. The method of producing lithium carbonate from lithium ore according to claim 1, characterized by, In step S3, the proportion of particles with a size of-74 μm in the ground material is 75-85 wt%.

3. The method of producing lithium carbonate from lithium ores according to claim 2, characterized in that, The mass ratio of the ground material to the leaching agent is 1:(1-2), and the leaching time is 30-40 min.

4. The method of producing lithium carbonate from lithium ore according to claim 1, characterized by, In step S4, the aluminum removal by extraction is performed using an organic phase containing di(2-ethylhexyl) phosphate at a pH value of 2.5-3.

5.

5. The method of producing lithium carbonate from lithium ore according to claim 4, characterized in that, The iron removal is performed at a pH value of 3.5-4.5; and the fluorine, calcium, and magnesium removal is performed at a pH value of 11-12.

6. The method of producing lithium carbonate from lithium ore according to claim 1, characterized by, In step S5, the lithium enrichment by extraction is performed using an organic phase containing β-diketone main extractant and phosphine oxide auxiliary extractant at a pH value not lower than 12.

5.

7. The method of producing lithium carbonate from lithium ore according to claim 6, characterized in that, The back extraction uses sulfuric acid with a concentration of 1-3 mol / L as back extraction agent.

8. The method of producing lithium carbonate from lithium ore according to claim 1, characterized by, The raffinate produced in step S5 is also concentrated and evaporated to obtain sodium sulfate heptahydrate byproduct.

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