A method for extracting lithium from spodumene to produce lithium carbonate

Abstract

The application provides a method for preparing lithium carbonate by extracting lithium from spodumene, and belongs to the technical field of lithium carbonate preparation; the preparation process comprises the following steps: preparation of modified chelating resin; preparation of lithium-containing leaching solution; purification and impurity removal; lithium precipitation to prepare lithium carbonate. The preparation process does not contain sulfation roasting, and the spodumene is not subjected to high-temperature transformation roasting alone, so that lithium carbonate with high purity can be finally prepared, the problems of high energy consumption and large sulfuric acid consumption in the lithium extraction process of the spodumene concentrate by the sulfuric acid method in the prior art are solved, the impurity crystals are precipitated by gradually reducing the temperature, preliminary impurity removal is performed, and then the lithium-containing leaching solution is subjected to secondary impurity removal and deep impurity removal by the cation chelating resin and the modified chelating resin, so that the purification effect is improved, and the purity of the lithium carbonate is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium carbonate preparation technology, and specifically to a method for preparing lithium carbonate by extracting lithium from spodumene. Background Technology

[0002] Lithium exists in various compounds in nature. Among them, lithium carbonate, as the most important basic lithium salt, is the basic raw material for producing other lithium compounds such as lithium metal, lithium chloride, lithium molybdate, and butyllithium. It can be used to prepare lithium-ion batteries, as an electrolytic bath additive in aluminum smelting, and is also widely used in industries such as glass, ceramics, medicine, and food.

[0003] Spodumene, as the most important lithium-containing mineral, has a high Li₂O content and few impurities, making it the main raw material for producing lithium carbonate from ore lithium resources. The main methods for extracting lithium carbonate from spodumene include sulfuric acid roasting, limestone sintering, chlorination roasting, and pressure cooking. The sulfuric acid roasting method is the most common method for lithium extraction from spodumene. This method involves roasting the α-spodumene in the spodumene concentrate at high temperatures to convert it into β-spodumene. The calcined β-spodumene is then ground and mixed with concentrated sulfuric acid for further roasting. This double roasting process consumes a significant amount of energy and acid, resulting in the formation of large quantities of unusable sulfates, which pollute the environment.

[0004] Therefore, we propose a method for extracting lithium from spodumene to prepare lithium carbonate, which solves the problems of high energy consumption and large sulfuric acid consumption in the existing spodumene concentrate sulfuric acid extraction process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, a method for extracting lithium from spodumene to prepare lithium carbonate is proposed, which solves the problems of high energy consumption and large sulfuric acid consumption in the existing lithium extraction process using spodumene concentrate via sulfuric acid.

[0006] A method for extracting lithium from spodumene to prepare lithium carbonate includes the following steps: S1: Preparation of modified chelating resin Chitosan powder was dissolved in acetic acid solution, sodium hydroxide solution was added, and after standing, washing and drying, it was placed in isopropanol solution, pH was adjusted, epichlorohydrin was added, the reaction was filtered and washed, and then placed in a mixed solution of dioxane and sodium hydroxide. N-methyl-D-glucosamine was added, and after the reaction, the mixture was filtered and washed to obtain the modified chelating resin. S2: Preparation of lithium-containing leachate After crushing, grinding, and screening, spodumene concentrate is mixed with coal gangue, and calcium chloride, sodium carbonate and polymethyl methacrylate are added to form pellets. After drying, the pellets are roasted. The roasted spodumene pellets are then leached with water at room temperature and filtered to obtain a lithium-containing leachate. S3: Purification and Impurity Removal The lithium-containing leachate was heated and the pH was adjusted. It was then cooled and filtered twice to obtain a lithium-containing leachate with preliminary impurity removal. A cationic chelating resin was added and mixed and filtered to obtain a lithium-containing leachate with secondary impurity removal. A modified chelating resin was then added and mixed and filtered to obtain a lithium-containing leachate with deep impurity removal. S4: Lithium carbonate preparation by lithium precipitation Sodium carbonate was added to the lithium-containing leachate that had been thoroughly purified, and the solution was allowed to stand, filtered, washed, filtered again, and dried to obtain lithium carbonate.

[0007] Furthermore, the preparation of the modified chelating resin in step S1 specifically includes the following steps: S1.1: Dissolve 2-3 parts of chitosan powder in 40-60 parts of 8wt% acetic acid solution, then add 5-8 parts of sodium hydroxide solution, let stand for 10-12 hours, wash with deionized water until neutral, and dry to harden to form chitosan particles. S1.2: Place 2-3 parts of chitosan particles into 50-60 parts of 60wt% isopropanol solution, adjust the pH to 9-10, add 10-15 parts of epichlorohydrin, heat to 50-70℃, reflux for 3-5 hours, then filter, wash with water and ethanol 3-5 times to obtain chlorinated cross-linked chitosan particles. S1.3: Take 100-120 parts of dioxane, add 40-50 parts of 80wt% sodium hydroxide solution, and mix well to obtain a mixed solution of dioxane and sodium hydroxide; S1.4: Place 2-3 parts of chlorinated cross-linked chitosan particles in a mixed solution of 130-140 parts of dioxane and sodium hydroxide, add 30-40 parts of N-methyl-D-glucosamine, heat to 50-70℃, reflux for 3-5 hours, then filter, and wash with water and ethanol 3-5 times to obtain the modified chelating resin.

[0008] Further, step S2 prepares a lithium-containing leachate, specifically including the following steps: S2.1: Crushing, grinding and sieving spodumene concentrate to obtain ore powder; S2.2: Add 1-3 parts of coal gangue to 10-20 parts of ore powder, mix, then add 1-3 parts of calcium chloride, 2-4 parts of sodium carbonate and 2-3 parts of polymethyl methacrylate. Grind and mix evenly, then add water to form pellets and dry them in an oven to obtain spodumene pellets. S2.3: The spodumene pellets are placed into a roasting device for roasting to obtain roasted spodumene pellets; S2.4: Take 10-20 parts of calcined spodumene pellets, add 20-40 parts of water, leach at room temperature for 30-40 minutes, and filter to obtain lithium-containing leachate.

[0009] Furthermore, step S3, purification and impurity removal, specifically includes the following steps: S3.1: Heat the lithium-containing leachate to 50-55℃, add sodium hydroxide solution, adjust the pH to 11.5-12, and then gradually cool and filter in two stages to obtain the lithium-containing leachate after preliminary impurity removal; S3.2: Mix 10-20 parts of the lithium-containing leachate after preliminary impurity removal with 20-30 parts of cationic chelating resin, react for 1-2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate after secondary impurity removal. S3.3: Mix 10-20 parts of the lithium-containing leachate after secondary impurity removal with 20-30 parts of modified chelating resin, react for 1-2 hours, filter, collect the filtrate, and obtain a deeply impurity-removed lithium-containing leachate.

[0010] Further, step S4, lithium precipitation to prepare lithium carbonate, specifically includes the following steps: S4.1: Add 20-30 parts of sodium carbonate to 10-20 parts of deeply purified lithium-containing leachate, stir, let stand, and then filter to obtain crude lithium carbonate. S4.2: Wash the crude lithium carbonate with deionized water 2-3 times, filter, and dry to obtain lithium carbonate.

[0011] Furthermore, the sodium hydroxide solution in step S1.1 is a 38-42 wt% sodium hydroxide solution.

[0012] Furthermore, the sodium hydroxide solution in step S1.3 is a 78-82 wt% sodium hydroxide solution.

[0013] Furthermore, the particle size after sieving in step S2.1 is 175-180 μm.

[0014] Furthermore, in step S2.3, the calcination temperature is 850-1050℃ and the calcination time is 10-20h.

[0015] Furthermore, the two-stage gradual cooling filtration in step S3.1 is as follows: cooling to 10-12℃ at 2-2.5℃ / min, filtering, and then cooling to 0℃ again at 1.5-2℃ / min, filtering.

[0016] Compared with the prior art, the present invention has at least one of the following beneficial technical effects: 1. The preparation process of this invention does not involve sulfation roasting, and spodumene does not undergo high-temperature transformation roasting alone. In the end, high-purity lithium carbonate can be obtained, which solves the problems of high energy consumption and large sulfuric acid consumption in the existing lithium extraction process of spodumene concentrate. By gradually cooling, impurity crystals are precipitated for preliminary impurity removal. Then, cation chelating resin and modified chelating resin are used to perform secondary and deep impurity removal on the lithium-containing leachate, thereby improving the purification effect and increasing the purity of lithium carbonate.

[0017] 2. This invention enhances the stability and mechanical strength of chitosan particles by subjecting them to a chlorination cross-linking reaction. By grafting N-methyl-D-glucosamine as an adsorption functional group onto the chlorinated cross-linked chitosan particle matrix, the adsorption capacity of the chelating resin can be improved, thereby increasing the adsorption of boron ions, calcium ions, and magnesium ions, reducing the content of impurities, and improving the purity of lithium carbonate.

[0018] 3. By mixing coal gangue with spodumene, this invention facilitates the uniform roasting of spodumene and also helps to form the mixed material into pellets. Forming the mixed material into pellets makes the roasting of spodumene more uniform, avoids problems such as local sintering or uneven reaction, and helps to improve the leaching rate of lithium ions.

[0019] 4. This invention adds calcium chloride, sodium carbonate, and polymethyl methacrylate during roasting. Calcium chloride can destroy the original stable chemical structure of spodumene ore powder. At the same time, the addition of calcium chloride and sodium carbonate can improve the corrosion and environmental pollution caused by chloride salt roasting. During the roasting process, calcium chloride undergoes oxidative decomposition, which plays a role in decomposing spodumene minerals. The addition of sodium carbonate can increase the lithium leaching rate. The addition of polymethyl methacrylate can create pores inside the lithium ore powder, which is more conducive to the decomposition of lithium ore powder during roasting and improves the lithium ion leaching rate. Attached Figure Description

[0020] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the present disclosure and, together with the specification, further serve to explain the principles of the present disclosure and enable those skilled in the art to implement and use the present disclosure.

[0021] Figure 1 This is a process flow diagram of a method for preparing lithium carbonate from spodumene using an embodiment of the present invention; Figure 2 This is a comparative table showing the lithium carbonate content, calcium ion content, magnesium ion content, and boron content of Examples 1-3 and Comparative Examples 1-2 of the present invention. Figure 3 This is a comparative table showing the lithium leaching rates of Examples 1-3 and Comparative Examples 3-4 of the present invention. Detailed Implementation

[0022] The method for extracting lithium from spodumene to prepare lithium carbonate according to the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention. Example

[0023] A method for extracting lithium from spodumene to prepare lithium carbonate, such as Figure 1 As shown, it includes the following steps: S1: Preparation of modified chelating resin S1.1: Dissolve 2 parts of chitosan powder in 40 parts of 8wt% acetic acid solution, then add 5 parts of 40wt% sodium hydroxide solution, let stand for 10 hours, wash with deionized water until neutral, and dry to harden to form chitosan particles. S1.2: Place 2 parts of chitosan particles into 50 parts of 60wt% isopropanol solution, adjust the pH to 9, add 10 parts of epichlorohydrin, heat to 50℃, reflux for 3h, then filter, wash 3 times with water and ethanol to obtain chlorinated cross-linked chitosan particles. S1.3: Take 100 parts of dioxane, add 40 parts of 80wt% sodium hydroxide solution, and mix well to obtain a mixed solution of dioxane and sodium hydroxide; S1.4: Place 2 parts of chlorinated cross-linked chitosan particles in a mixed solution of 130 parts of dioxane and sodium hydroxide, add 30 parts of N-methyl-D-glucosamine, heat to 50°C, reflux for 3 hours, then filter, and wash three times with water and ethanol to obtain the modified chelating resin.

[0024] S2: Preparation of lithium-containing leachate S2.1: Crushing, grinding, and sieving spodumene concentrate to a particle size of 175μm to obtain ore powder; S2.2: Add 1 part coal gangue to 10 parts ore powder, mix, then add 1 part calcium chloride, 2 parts sodium carbonate and 2 parts polymethyl methacrylate, grind and mix evenly, add water to form pellets, place in an oven to dry, and obtain spodumene pellets. S2.3: The spodumene pellets are placed into a calcining device for calcination at a temperature of 850°C for 10 hours to obtain calcined spodumene pellets. S2.4: Take 10 parts of calcined spodumene pellets, add 20 parts of water, leach at room temperature for 30 minutes, and filter to obtain lithium-containing leachate.

[0025] S3: Purification and Impurity Removal S3.1: Heat the lithium-containing leachate to 50°C, add sodium hydroxide solution to adjust the pH to 11.5, then cool it down to 10°C at 2°C / min, filter it, and then cool it down to 0°C again at 1.5°C / min, filter it, and obtain the lithium-containing leachate after preliminary impurity removal. S3.2: Mix 10 parts of the lithium-containing leachate after preliminary impurity removal with 20 parts of cationic chelating resin, react for 1-2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate after secondary impurity removal; S3.3: Mix 10 parts of the lithium-containing leachate that has undergone secondary impurity removal with 20 parts of the modified chelating resin, react for 1-2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate that has undergone deep impurity removal.

[0026] S4: Lithium carbonate preparation by lithium deposition S4.1: Add 20 parts of sodium carbonate to 10 parts of deeply purified lithium-containing leachate, stir, let stand, and then filter to obtain crude lithium carbonate. S4.2: Wash the crude lithium carbonate twice with deionized water, filter, and dry to obtain lithium carbonate. Example

[0027] A method for extracting lithium from spodumene to prepare lithium carbonate, such as Figure 1 As shown, it includes the following steps: S1: Preparation of modified chelating resin S1.1: Dissolve 3 parts of chitosan powder in 60 parts of 8wt% acetic acid solution, then add 8 parts of 40wt% sodium hydroxide solution, let stand for 10 hours, wash with deionized water until neutral, and dry to harden to form chitosan particles. S1.2: Place 3 parts of chitosan particles into 60 parts of 60wt% isopropanol solution, adjust the pH to 10, add 15 parts of epichlorohydrin, heat to 50℃, reflux for 3h, then filter, wash 3 times with water and ethanol to obtain chlorinated cross-linked chitosan particles. S1.3: Take 120 parts of dioxane, add 50 parts of 80wt% sodium hydroxide solution, and mix well to obtain a mixed solution of dioxane and sodium hydroxide; S1.4: Place 3 parts of chlorinated cross-linked chitosan particles in a mixed solution of 140 parts of dioxane and sodium hydroxide, add 40 parts of N-methyl-D-glucosamine, heat to 50°C, reflux for 3 hours, then filter, and wash three times with water and ethanol to obtain the modified chelating resin.

[0028] S2: Preparation of lithium-containing leachate S2.1: Crushing, grinding, and sieving spodumene concentrate to a particle size of 175μm to obtain ore powder; S2.2: Add 3 parts of coal gangue to 20 parts of ore powder, mix, then add 3 parts of calcium chloride, 4 parts of sodium carbonate and 3 parts of polymethyl methacrylate, grind and mix evenly, add water to form pellets, place in an oven to dry, and obtain spodumene pellets. S2.3: The spodumene pellets are placed into a calcining device for calcination at a temperature of 850°C for 20 hours to obtain calcined spodumene pellets. S2.4: Take 20 parts of calcined spodumene pellets, add 40 parts of water, leach at room temperature for 30 minutes, and filter to obtain lithium-containing leachate.

[0029] S3: Purification and Impurity Removal S3.1: Heat the lithium-containing leachate to 50°C, add sodium hydroxide solution to adjust the pH to 11.5, then cool it down to 10°C at 2°C / min, filter it, and then cool it down to 0°C again at 1.5°C / min, filter it, and obtain the lithium-containing leachate after preliminary impurity removal. S3.2: Mix 20 parts of the lithium-containing leachate after preliminary impurity removal with 30 parts of cationic chelating resin, react for 1 hour, filter, collect the filtrate, and obtain the lithium-containing leachate after secondary impurity removal; S3.3: Mix 20 parts of the lithium-containing leachate that has undergone secondary impurity removal with 30 parts of the modified chelating resin, react for 2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate that has undergone deep impurity removal.

[0030] S4: Lithium carbonate preparation by lithium deposition S4.1: Add 30 parts of sodium carbonate to 20 parts of deeply purified lithium-containing leachate, stir, let stand, and then filter to obtain crude lithium carbonate. S4.2: Wash the crude lithium carbonate twice with deionized water, filter, and dry to obtain lithium carbonate. Example

[0031] A method for extracting lithium from spodumene to prepare lithium carbonate, such as Figure 1 As shown, it includes the following steps: S1: Preparation of modified chelating resin S1.1: Dissolve 2 parts of chitosan powder in 40 parts of 8wt% acetic acid solution, then add 5 parts of 40wt% sodium hydroxide solution, let stand for 12 hours, wash with deionized water until neutral, and dry to harden to form chitosan particles. S1.2: Place 2 parts of chitosan particles into 50 parts of 60wt% isopropanol solution, adjust the pH to 10, add 10 parts of epichlorohydrin, heat to 70℃, reflux for 5h, then filter, wash 5 times with water and ethanol to obtain chlorinated cross-linked chitosan particles. S1.3: Take 100 parts of dioxane, add 40 parts of 80wt% sodium hydroxide solution, and mix well to obtain a mixed solution of dioxane and sodium hydroxide; S1.4: Place 2 parts of chlorinated cross-linked chitosan particles in a mixed solution of 130 parts of dioxane and sodium hydroxide, add 30 parts of N-methyl-D-glucosamine, heat to 70°C, reflux for 3 hours, then filter, and wash 5 times with water and ethanol to obtain the modified chelating resin.

[0032] S2: Preparation of lithium-containing leachate S2.1: Crushing, grinding, and sieving spodumene concentrate to a particle size of 180μm to obtain ore powder; S2.2: Add 1 part coal gangue to 10 parts ore powder, mix, then add 1 part calcium chloride, 2 parts sodium carbonate and 2 parts polymethyl methacrylate, grind and mix evenly, add water to form pellets, place in an oven to dry, and obtain spodumene pellets. S2.3: The spodumene pellets are placed into a calcining device for calcination at a temperature of 1050℃ for 10 hours to obtain calcined spodumene pellets. S2.4: Take 10 parts of calcined spodumene pellets, add 20 parts of water, leach at room temperature for 40 minutes, and filter to obtain lithium-containing leachate.

[0033] S3: Purification and Impurity Removal S3.1: Heat the lithium-containing leachate to 55°C, add sodium hydroxide solution to adjust the pH to 12, then cool it down to 12°C at 2.5°C / min, filter it, and then cool it down to 0°C again at 2°C / min, filter it again to obtain the lithium-containing leachate after preliminary impurity removal. S3.2: Mix 10 parts of the lithium-containing leachate after preliminary impurity removal with 20 parts of cationic chelating resin, react for 2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate after secondary impurity removal; S3.3: Mix 10 parts of the lithium-containing leachate that has undergone secondary impurity removal with 20 parts of the modified chelating resin, react for 2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate that has undergone deep impurity removal.

[0034] S4: Lithium carbonate preparation by lithium deposition S4.1: Add 20 parts of sodium carbonate to 10 parts of deeply purified lithium-containing leachate, stir, let stand, and then filter to obtain crude lithium carbonate. S4.2: Wash the crude lithium carbonate three times with deionized water, filter, and dry to obtain lithium carbonate.

[0035] Compared with Example 1, Comparative Example 1 differs in that Comparative Example 1 uses commercially available lithium carbonate, specifically lithium carbonate sold by Henan Xiangfa Chemical Products Co., Ltd., and is referred to as Comparative Example 1.

[0036] Compared with Example 1, Comparative Example 2 differs in that steps 1 and S3.3 are removed, and the lithium-containing leaching solution with deep impurity removal in step S4.2 is replaced with an equal mass of lithium-containing leaching solution with secondary impurity removal. The remaining steps are unchanged in the preparation of lithium carbonate, and this is referred to as Comparative Example 2.

[0037] Performance testing The following performance tests were performed on the lithium carbonate in Examples 1-3 and Comparative Examples 1-2: Lithium carbonate content: The purity of lithium carbonate was determined according to GB / T11075-2013 "Lithium Carbonate". The test results are as follows: Figure 2 As shown.

[0038] Calcium ion content: The calcium ion content was determined according to GB / T11075-2013 "Lithium Carbonate". The test results are as follows: Figure 2 As shown.

[0039] Magnesium ion content: The magnesium ion content was determined according to GB / T11075-2013 "Lithium Carbonate". The test results are as follows: Figure 2 As shown.

[0040] Boron content: The boron content was determined according to YS / T582-2013 "Battery Grade Lithium Carbonate", and the test results are as follows. Figure 2 As shown.

[0041] from Figure 2 As can be seen from the examples and Comparative Example 1, the lithium carbonate prepared by the process of the examples has a similar lithium carbonate content to that of commercially available lithium carbonate, and the impurity content in the lithium carbonate is less, proving that the preparation process of the present invention can reduce the problems of high energy consumption and large sulfuric acid consumption.

[0042] from Figure 2 As can be seen from Examples and Comparative Example 2, the addition of modified chelating resin can improve the adsorption of boron ions, calcium ions, and magnesium ions, reduce the content of impurities, and improve the purity of lithium carbonate.

[0043] Compared with Example 1, Comparative Example 3 differs in that the coal gangue in step 2.2 is replaced with an equal mass of ore powder from step S2.1, while the remaining steps remain unchanged in the preparation of lithium carbonate, and is referred to as Comparative Example 3.

[0044] Compared with Example 1, Comparative Example 4 differs in that "1 part calcium chloride, 2 parts sodium carbonate and 2 parts polymethyl methacrylate" in step 2.2 is replaced with "4.2 parts sodium carbonate", while the other steps remain unchanged to prepare lithium carbonate, and it is referred to as Comparative Example 4.

[0045] The lithium-containing leachates obtained in step S3 of Examples 1-3 and Comparative Examples 3-4 were taken as samples, and the lithium ion content in the samples was detected by ICP-AES. The lithium leaching rate was calculated, and the detection results are as follows: Figure 3 As shown.

[0046] from Figure 3 As can be seen from Examples and Comparative Example 3, mixing coal gangue with spodumene is beneficial to improving the lithium ion leaching rate.

[0047] from Figure 3 As can be seen from Examples and Comparative Example 4, adding calcium chloride, sodium carbonate and polymethyl methacrylate during roasting facilitates the decomposition of lithium ore powder during roasting and improves the leaching rate of lithium ions.

[0048] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for extracting lithium from spodumene to prepare lithium carbonate, characterized in that, Includes the following steps: S1: Preparation of modified chelating resin S1.1: Dissolve 2-3 parts of chitosan powder in 40-60 parts of 8wt% acetic acid solution, then add 5-8 parts of sodium hydroxide solution, let stand for 10-12 hours, wash with deionized water until neutral, and dry to harden to form chitosan particles. S1.2: Place 2-3 parts of chitosan particles into 50-60 parts of 60wt% isopropanol solution, adjust the pH to 9-10, add 10-15 parts of epichlorohydrin, heat to 50-70℃, reflux for 3-5 hours, then filter, wash with water and ethanol 3-5 times to obtain chlorinated cross-linked chitosan particles. S1.3: Take 100-120 parts of dioxane, add 40-50 parts of 80wt% sodium hydroxide solution, and mix well to obtain a mixed solution of dioxane and sodium hydroxide; S1.4: Place 2-3 parts of chlorinated cross-linked chitosan particles in a mixed solution of 130-140 parts of dioxane and sodium hydroxide, add 30-40 parts of N-methyl-D-glucosamine, heat to 50-70℃, reflux for 3-5 hours, then filter, wash with water and ethanol 3-5 times to obtain the modified chelating resin. S2: Preparation of lithium-containing leachate S2.1: Crushing, grinding, and sieving spodumene concentrate to obtain ore powder; S2.2: Add 1-3 parts of coal gangue to 10-20 parts of ore powder, mix, then add 1-3 parts of calcium chloride, 2-4 parts of sodium carbonate and 2-3 parts of polymethyl methacrylate. Grind and mix evenly, then add water to form pellets and dry them in an oven to obtain spodumene pellets. S2.3: The spodumene pellets are placed into a roasting device for roasting to obtain roasted spodumene pellets; S2.4: Take 10-20 parts of calcined spodumene pellets, add 20-40 parts of water, leach at room temperature for 30-40 minutes, and filter to obtain lithium-containing leachate; S3: Purification and Impurity Removal S3.1: Heat the lithium-containing leachate to 50-55℃, add sodium hydroxide solution, adjust the pH to 11.5-12, and then gradually cool and filter in two stages to obtain the lithium-containing leachate after preliminary impurity removal; The two-stage gradual cooling filtration process is as follows: the temperature is lowered to 10-12℃ at a rate of 2-2.5℃ / min, and after filtration, the temperature is lowered again to 0℃ at a rate of 1.5-2℃ / min. S3.2: Mix 10-20 parts of the lithium-containing leachate after preliminary impurity removal with 20-30 parts of cationic chelating resin, react for 1-2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate after secondary impurity removal. S3.3: Mix 10-20 parts of the lithium-containing leachate after secondary impurity removal with 20-30 parts of modified chelating resin, react for 1-2 hours, filter, collect the filtrate, and obtain the lithium-containing leachate after deep impurity removal. S4: Lithium carbonate preparation by lithium precipitation Sodium carbonate was added to the lithium-containing leachate that had been thoroughly purified, and the solution was allowed to stand, filtered, washed, filtered again, and dried to obtain lithium carbonate.

2. The method for preparing lithium carbonate from spodumene according to claim 1, characterized in that, Step S4, lithium precipitation to prepare lithium carbonate, specifically includes the following steps: S4.1: Add 20-30 parts of sodium carbonate to 10-20 parts of deeply purified lithium-containing leachate, stir, let stand, and then filter to obtain crude lithium carbonate. S4.2: Wash the crude lithium carbonate with deionized water 2-3 times, filter, and dry to obtain lithium carbonate.

3. The method for extracting lithium from spodumene to prepare lithium carbonate according to claim 1, characterized in that, In step S1.1, the sodium hydroxide solution is a 38-42 wt% sodium hydroxide solution.

4. The method for preparing lithium carbonate from spodumene according to claim 1, characterized in that, The sodium hydroxide solution in step S1.3 is a 78-82 wt% sodium hydroxide solution.

5. The method for preparing lithium carbonate from spodumene according to claim 1, characterized in that, The particle size after sieving in step S2.1 is 175-180 μm.

6. The method for preparing lithium carbonate from spodumene according to claim 1, characterized in that, In step S2.3, the roasting temperature is 850-1050℃ and the roasting time is 10-20h.

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