Process for preparing lithium carbonate from lithium ore by wet method

Abstract

This invention discloses a process for preparing lithium carbonate from lithium ore using a hydrometallurgical method, relating to the field of hydrometallurgical technology. The process includes: adding lithium ore, sulfuric acid, and fluoride into a reaction vessel, heating, stirring, and filtering to obtain silicon slag and brine; adjusting the pH of the brine with alkali, adding potassium salt, stirring, cooling, and filtering to obtain alum and de-aluminated brine; adding phosphate and alkali to the de-aluminated brine, stirring, and filtering to obtain aluminum-fluoride slag and primary purified brine; adding lime to the primary purified brine, stirring, and filtering to obtain aluminum-calcium slag and secondary purified brine; adding sodium carbonate to the secondary purified brine, stirring, and filtering to obtain magnesium-calcium slag and tertiary purified brine; concentrating the tertiary purified brine, adding a saturated sodium carbonate solution for lithium precipitation, and obtaining lithium carbonate. This invention employs enhanced leaching to achieve low-temperature, atmospheric-pressure hydrometallurgical lithium extraction, resulting in high lithium recovery, low energy consumption, and the resource utilization of the aluminum-fluoride slag and alum generated during the lithium carbonate preparation process.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a process for the hydrometallurgical extraction of lithium from lithium ore to prepare lithium carbonate. Background Technology

[0002] Lithium, hailed as a "new energy metal," is an indispensable raw material for the development of the new energy industry, both its metal and compounds. Currently, industrially exploitable lithium resources can be categorized into brine-type and ore-type, with brine-type lithium mines accounting for approximately 64% and ore-type for about 36%. Although brine-type lithium resources are dominant in total quantity, and the cost of lithium extraction from brine is lower than from ore, limitations in extraction technology and mining environment have led to slow expansion of brine-based lithium extraction production. In the future, global ore-based and brine-based lithium extraction will coexist and develop in the long term. Therefore, research on lithium carbonate extraction processes from lithium ore is also of great significance.

[0003] There are approximately 145 known lithium-bearing minerals in nature, but the main ones with industrial mining value include spodumene, petalite, lepidolite, lepidolite, and phosphogypsum. Common methods for extracting lithium from ores include the sulfuric acid process, sulfate process, lime sintering process, chlorination calcination process, and soda ash pressure cooking process. Among these, the sulfuric acid process for producing lithium carbonate has advantages such as strong adaptability to raw materials, simple operation, and high recovery rate. However, in the acid process, other metals in the ore may react with the acid and enter the solution. Classifying and recycling these impurities presents technical difficulties and high costs.

[0004] Invention patent CN103145158B discloses a process for preparing lithium carbonate using sulfation roasting, caustic soda purification, and lithium carbide precipitation. This process uses concentrated sulfuric acid roasting at a reaction temperature of 200–300℃, resulting in lower energy consumption compared to traditional salt methods. However, it suffers from high acid consumption, difficult tail gas treatment, and air pollution. The impurity removal process uses caustic soda, which forms Li-Al layered bimetallic hydroxides (LDH, LiAl2(OH)7·2H2O), causing a large amount of lithium to enter the impurity removal residue, resulting in lithium loss. The literature "Fluorine Cyclic Acid Hydrolysis of Lithium Mica for Selective Leaching of Lithium" uses a hydrochloric acid system, introducing fluorides to achieve low-temperature lithium leaching (leaching temperature below 100℃). It also uses a cryolite method to reduce impurity concentration in the brine. However, this process suffers from problems such as the volatility of hydrochloric acid, high equipment corrosivity, the introduction of fluoride ions, incomplete impurity removal, and high precipitant consumption, making it difficult to directly obtain high-purity lithium carbonate products. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, this invention proposes a process for the wet extraction of lithium from lithium ore to prepare lithium carbonate. Potassium salts and fluoride salts are added to the lithium ore to enhance the leaching of lithium with sulfuric acid, thereby achieving low-temperature wet extraction of lithium at atmospheric pressure, with high lithium recovery rate and low energy consumption.

[0006] This invention proposes a process for preparing lithium carbonate from lithium ore using a wet process, comprising the following steps:

[0007] S1. Atmospheric pressure acid leaching: Lithium ore, sulfuric acid and fluoride are added to a reaction vessel, heated, stirred and reacted, filtered to obtain silicon slag and brine;

[0008] S2. Cooling and alum precipitation: Add alkali to adjust the pH of the brine, add potassium salt, stir to react, cool, and filter to obtain alum and de-alumened brine;

[0009] S3. Primary impurity removal: Add phosphate and alkali to the de-alumened brine, stir to react, filter, and obtain aluminum fluoride residue and primary purified brine;

[0010] S4. Secondary purification: Lime is added to the primary purified brine and stirred to react, resulting in aluminum-calcium slag and secondary purified brine.

[0011] S5. Three-stage purification: Sodium carbonate is added to the secondary purified brine and stirred to react, resulting in magnesium-calcium slag and tertiary purified brine.

[0012] S6. Concentration and Lithium Precipitation: The brine that has been purified three times is concentrated, and a saturated sodium carbonate solution is added to carry out a lithium precipitation reaction to obtain lithium carbonate.

[0013] Furthermore, in S1, the lithium ore is selected from one or more of lepidolite, lepidolite, lithium ceramic stone, and lithium aluminum phosphate.

[0014] The sulfuric acid has a mass percentage concentration of 5% to 50%; the solid-liquid ratio in the reaction vessel is 0.5 to 4:1.

[0015] The fluoride is selected from one or more of sodium fluoride, calcium fluoride, potassium fluoride, aluminum fluoride, hydrogen fluoride, and fluorosilicic acid; the amount of fluoride added is 0.1 to 1 times the total molar amount of aluminum in the lithium ore;

[0016] The temperature of the stirring reaction is 30–100℃, the stirring speed is 100–600 r / min, and the reaction time is 2–12 h.

[0017] Furthermore, S1 also includes the simultaneous addition of potassium salt to the reactor;

[0018] The potassium salt is one or more of potassium sulfate, potassium chloride, potassium nitrate, and potassium phosphate;

[0019] The amount of potassium salt added is 0 to 10% of the weight of lithium ore.

[0020] Further, in S2, an alkali is added to adjust the pH of the brine to 0-2; the alkali is selected from potassium hydroxide and / or sodium hydroxide;

[0021] The potassium salt is selected from one or more of potassium sulfate, potassium chloride, potassium nitrate, and potassium phosphate; the potassium salt is added to adjust the potassium-aluminum molar ratio in the brine to 0.5-1.1:1.

[0022] Furthermore, in S2, the mixture is stirred at 40–70°C for 20–120 min, and then cooled to 0–10°C for 20–80 min to crystallize.

[0023] Further, in S3, the phosphate is selected from one or more of sodium phosphate, potassium phosphate, ammonium phosphate, diammonium hydrogen phosphate, and calcium phosphate; the amount of phosphate used is 0.8 to 1.2 times the molar amount of aluminum in the alum-removing brine;

[0024] The alkali is sodium hydroxide, and the pH of the system is adjusted to 3.0–4.5 by adding alkali.

[0025] Furthermore, in S3, the temperature of the stirred reaction is 20–90°C, and the reaction time is 0.5–3 h;

[0026] The resulting aluminum fluoride slag is returned to the lithium ore acid leaching process in S1.

[0027] Furthermore, in S4, the amount of lime added is 30–100 kg / m³, based on the volume of brine purified in one step. 3 ;

[0028] The temperature of the stirring reaction is 50–80℃, the reaction time is 0.5–3h, and the stirring speed is 100–600r / min.

[0029] Furthermore, in step S5, the amount of sodium carbonate added is 1.0 to 1.2 times the molar amount of calcium in the secondary purified brine; the concentration of the sodium carbonate solution is 200 g / L to 300 g / L.

[0030] The stirring reaction time is 0.5 to 3 hours, and the reaction temperature is 10 to 50°C.

[0031] Further, in S6, the sodium carbonate is added in solution form, and the amount of sodium carbonate added is 1.0 to 1.5 times the molar amount of lithium in the three-stage purified brine based on the volume of the brine; the concentration of the sodium carbonate solution is 200 g / L to 300 g / L.

[0032] The lithium precipitation reaction is carried out at a temperature of 80–100°C and an aging time of 1–5 hours.

[0033] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0034] 1. This invention, based on the traditional sulfuric acid process for lithium extraction, incorporates potassium and fluoride salts to synergistically enhance the lithium extraction process. Potassium salts promote the substitution (electrochemical) of lithium ions in mica minerals, while fluorides utilize their complexation with aluminum to promote mineral structure disruption. The entire leaching process is characterized by mild conditions, low energy consumption, and good adaptability to low-grade ores such as lepidolite, lepidolite, lithium pyroxene, and lithium aluminum phosphate, achieving a lithium leaching rate greater than 95%.

[0035] 2. This invention uses cooling and precipitation to obtain alkali metal alum containing potassium, rubidium, cesium, etc., thereby turning impurities such as potassium, rubidium, cesium, and aluminum in the brine into resources, improving the resource utilization of lithium ore, avoiding resource waste, and effectively reducing the load and slag volume of subsequent impurity removal processes.

[0036] 3. This invention uses phosphate and lime to remove impurities such as iron, aluminum, and fluorine from the fluorine-based lithium extraction leaching solution in lithium ore. It systematically solves the technical problems of high impurity content in the low-temperature acid lithium extraction leaching solution and large lithium loss during the impurity removal process. Furthermore, the aluminum-fluorine slag obtained from the impurity removal process can be reused in the leaching process.

[0037] This invention employs an enhanced leaching method to achieve low-temperature, atmospheric-pressure wet lithium extraction, which boasts advantages such as high lithium recovery rate and low energy consumption. Furthermore, the aluminum fluoride slag and alum generated during lithium carbonate preparation can be utilized as resources, eliminating problems such as fluorine pollution from traditional sulfuric acid roasting of lithium ore and the waste of valuable resources like aluminum, rubidium, and cesium in the ore, aligning with my country's concept of developing a green economy. Attached Figure Description

[0038] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0039] like Figure 1 As shown, Figure 1 This is a process flow diagram of the present invention.

[0040] The technical solution of the present invention will now be described in detail through specific embodiments.

[0041] Example 1

[0042] One lithium-bearing ore is lepidolite, with the chemical formula K{Li 2-x Al 1+x [Al 2x Si 4-2x O 10 The main chemical components of the compound are: Li₂O ~ 3.3%, Na₂O ~ 2.1%, Al₂O₃ ~ 21.8%, SiO₂ ~ 48.44%, Fe₂O₃ ~ 0.18%, K₂O ~ 6.7%, CaO ~ 0.8%, and MgO ~ 0.23%.

[0043] The process flow for preparing lithium carbonate from lepidolite is as follows: Figure 1 As shown, the specific operation is as follows:

[0044] Take 1.2 kg of lithium ore, 40 g of calcium fluoride, and 30 g of potassium sulfate, and add them sequentially to 2.2 L of 25% sulfuric acid. Heat in a water bath to 95°C, stirring at 300 r / min, and react for 6 hours. After the reaction is complete, filter and wash with water; the volume of the brine is measured to be 2.4 L, and the composition is K. + ~18.38g / L, Li2O ~16.3g / L, Al 3+ ~34.1 g / L, Fe 2+ ~1.3g / L, Ca 2+ ~0.48 g / L, Mg 2+ ~0.35g / L, Mn 2+ ~0.41g / L, F - ~9.2 g / L. On a liquid basis, the lithium leaching rate of this lepidolite is 98.8%.

[0045] Take 2.0 L of lithium-extraction brine obtained from lithium mica acidification, adjust its pH to 2.0 with potassium hydroxide, add 80 g of potassium sulfate, and stir at 60℃ for 20 min. Then place it in a refrigeration unit, adjust the temperature to 5℃, and stir slowly for 30 min to obtain alum and 1.9 L of de-alumened brine. Lithium is essentially not lost in this process, and the main component of the de-alumened brine is potassium (K). + ~8.4g / L, Li2O ~17.15g / L, Al 3+ ~13.07g / L, Fe 3+ ~1.37g / L, Ca 2+ ~0.51g / L, Mg 2+ ~0.38g / L, Mn 2+ ~0.44g / L, F - ~9.6g / L.

[0046] Add 95g of sodium phosphate to the alum-removing brine. After the sodium phosphate is fully dissolved, adjust the pH of the aqueous leaching solution to 4.5 using caustic soda flakes. The reaction temperature is 85℃, and the reaction time is 1.0 h. After settling and filtration, primary impurity-removed brine and aluminum fluoride slag are obtained. The main component of the primary impurity-removed brine is potassium (K). + ~8.3g / L, Li2O ~16.98g / L, Al 3+ ~0.42g / L, Fe 3+ ~ND, Ca 2+ ~0.37g / L, Mg 2+ ~0.34g / L, Mn 2+ ~0.40g / L, F - ~0.35g / L.

[0047] 100g of quicklime was added to the primary purified brine, and the mixture was reacted at 60℃ for 1.5 hours. After the reaction, the brine was filtered to obtain the secondary purified brine. At this point, all impurities such as aluminum, iron, magnesium, manganese, and fluorine in the brine were removed, and the main residue was potassium (K). + ~8.3g / L, Ca 2+ ~2.0 g / L. The brine, after secondary impurity removal, was subjected to a three-stage impurity removal process using a 200 g / L sodium carbonate solution (55 mL added). After reacting for 0.5 h, the mixture was filtered to obtain purified brine and magnesium-calcium slag. Testing revealed that impurities such as aluminum, iron, fluorine, and manganese in the purified brine were all below 5 mg / L, and impurities such as calcium and magnesium were below 15 mg / L. On a liquid basis, the lithium loss rate during impurity removal in this example was 4.6%.

[0048] 1.9 L of purified brine was concentrated by evaporation to a Li₂O concentration of approximately 25 g / L. A saturated sodium carbonate solution was prepared, and 1.2 times the molar amount of lithium ions of sodium carbonate was added using a reverse addition method. The precipitation reaction was carried out at 90 °C. After aging for 2 hours, the solution was washed twice with deionized water at 90 °C and dried to obtain 64.42 g of lithium carbonate product. The primary precipitation rate was 81.2%, and the lithium carbonate composition was: Li₂O₃–98.64%, K–0.76%, Na–0.19%, Ca–0.0069%, Mg–0.0019%, Fe–0.0014%, Al–0.0049%, Mn–0.012%.

[0049] Excluding lithium in the lithium precipitation mother liquor, the lithium yield of this process is greater than 88% throughout the entire process.

[0050] Example 2

[0051] One lithium-bearing ore is lepidolite, with the chemical formula K{Li 2-x Al 1+x [Al 2x Si 4-2x O 10 The main chemical components of the compound are: Li₂O ~ 3.3%, Na₂O ~ 2.1%, Al₂O₃ ~ 21.8%, SiO₂ ~ 48.44%, Fe₂O₃ ~ 0.18%, K₂O ~ 6.7%, CaO ~ 0.8%, and MgO ~ 0.23%.

[0052] The process flow for preparing lithium carbonate from lepidolite is as follows: Figure 1 As shown, the specific operation is as follows:

[0053] Take 1.2 kg of lithium ore, 35 g of calcium fluoride, and 25 g of potassium sulfate, and add them sequentially to 2.2 L of 25% sulfuric acid. Heat in a water bath to 95°C, stirring at 300 r / min, and react for 6 hours. After the reaction is complete, filter and wash with water; the volume of the brine is measured to be 2.4 L, and its composition is K.+ ~13.51g / L, Li2O ~16.2g / L, Al 3+ ~33.9 g / L, Fe 2+ ~1.3g / L, Ca 2+ ~0.45g / L, Mg 2+ ~0.37g / L, Mn 2+ ~0.40g / L, F - ~8.7 g / L. On a liquid basis, the lithium leaching rate of this lepidolite is 98.1%.

[0054] Take 2.0 L of lithium-extraction brine obtained from lithium mica acidification, adjust its pH to 1.5 with potassium hydroxide, add 90 g of potassium sulfate, and stir at 60℃ for 20 min. Then place it in a refrigeration unit, adjust the temperature to 3℃, and stir slowly for 40 min to obtain alum and 1.9 L of de-alumened brine. Lithium is essentially not lost in this process, and the main component of the de-alumened brine is potassium (K). + ~7.9g / L, Li2O ~17.10g / L, Al 3+ ~10.0g / L, Fe 3+ ~1.33g / L, Ca 2+ ~0.48 g / L, Mg 2+ ~0.40g / L, Mn 2+ ~0.43g / L, F - ~9.1g / L.

[0055] Add 85g of sodium phosphate to the alum-removing brine. After the sodium phosphate is fully dissolved, adjust the pH of the aqueous leaching solution to 4.5 using caustic soda flakes. The reaction temperature is 85℃, and the reaction time is 1.0 h. After settling and filtration, primary impurity-removed brine and aluminum fluoride residue are obtained. The main component of the primary impurity-removed brine is potassium (K). + ~7.8g / L, Li2O ~16.99g / L, Al 3+ ~0.31g / L, Fe 3+ ~ND, Ca 2+ ~0.38g / L, Mg 2+ ~0.33g / L, Mn 2+ ~0.39g / L, F - ~0.30g / L.

[0056] 90g of quicklime was added to the primary purified brine, and the mixture was reacted at 60℃ for 1.5 hours. After the reaction, the brine was filtered to obtain the secondary purified brine. At this point, all impurities such as aluminum, iron, magnesium, manganese, and fluorine in the brine were removed, and the main residue was potassium (K). + ~7.9g / L, Ca 2+~1.9 g / L. The brine, after secondary impurity removal, was subjected to a three-stage impurity removal process using a 200 g / L sodium carbonate solution (50 mL added). After reacting for 0.5 h, the mixture was filtered to obtain purified brine and magnesium-calcium slag. Testing revealed that impurities such as aluminum, iron, fluorine, and manganese in the purified brine were all below 5 mg / L, and impurities such as calcium and magnesium were below 15 mg / L. On a liquid basis, the lithium loss rate during impurity removal in this example was 4.4%.

[0057] 1.9 L of purified brine was concentrated by evaporation to a Li₂O concentration of approximately 25 g / L. A saturated sodium carbonate solution was prepared, and 1.1 times the molar amount of lithium ions of sodium carbonate was added using a reverse addition method. The precipitation reaction was carried out at 90 °C. After aging for 2 hours, the solution was washed twice with deionized water at 90 °C and dried to obtain 63.37 g of lithium carbonate product. The primary precipitation rate was 80.8%, and the lithium carbonate composition was: Li₂O₃–98.61%, K–0.74%, Na–0.21%, Ca–0.007%, Mg–0.002%, Fe–0.002%, Al–0.005%, Mn–0.009%.

[0058] Excluding lithium in the lithium precipitation mother liquor, the lithium yield of this process is greater than 88% throughout the entire process.

[0059] Example 3

[0060] One lithium-bearing ore is lepidolite, with the chemical formula K{Li 2-x Al 1+x [Al 2x Si 4-2x O 10 The main chemical components of the compound are: Li₂O ~ 3.3%, Na₂O ~ 2.1%, Al₂O₃ ~ 21.8%, SiO₂ ~ 48.44%, Fe₂O₃ ~ 0.18%, K₂O ~ 6.7%, CaO ~ 0.8%, and MgO ~ 0.23%.

[0061] Take 1.2 kg of lithium ore, 30 g of calcium fluoride, and 20 g of potassium sulfate, and add them sequentially to 2.2 L of 25% sulfuric acid. Heat in a water bath to 90°C, stirring at 250 r / min, and react for 4 h. After the reaction is complete, filter and wash with water; the volume of the brine is measured to be 2.4 L, and its composition is K. + ~11.14g / L, Li2O ~15.96g / L, Al 3+ ~32.7g / L, Fe 2+ ~1.2g / L, Ca 2+ ~0.43 g / L, Mg 2+ ~0.39g / L, Mn 2+ ~0.41g / L, F -~7.4 g / L. On a liquid basis, the lithium leaching rate of this lepidolite is 96.7%.

[0062] Take 2.0 L of lithium-extraction brine obtained from lithium mica acidification, adjust its pH to 1.0 with potassium hydroxide, add 100 g of potassium sulfate, and stir at 60℃ for 25 min. Then place it in a refrigeration unit, adjust the temperature to 2℃, and stir slowly for 40 min to obtain alum and 1.9 L of de-alumened brine. Lithium is essentially not lost in this process, and the main component of the de-alumened brine is potassium (K). + ~7.3g / L, Li2O ~16.80g / L, Al 3+ ~9.1 g / L, Fe 3+ ~1.32g / L, Ca 2+ ~0.49 g / L, Mg 2+ ~0.47g / L, Mn 2+ ~0.45g / L, F - ~7.8g / L.

[0063] Add 80g of sodium phosphate to the alum-removing brine. After the sodium phosphate is fully dissolved, adjust the pH of the aqueous leaching solution to 4.5 using caustic soda flakes. The reaction temperature is 85℃, and the reaction time is 1.0 h. After settling and filtration, primary impurity-removed brine and aluminum fluoride residue are obtained. The main component of the primary impurity-removed brine is potassium (K). + ~7.1g / L, Li2O ~16.71g / L, Al 3+ ~0.29g / L, Fe 3+ ~ND, Ca 2+ ~0.35g / L, Mg 2+ ~0.36g / L, Mn 2+ ~0.38g / L, F - ~0.27g / L.

[0064] 85g of quicklime was added to the primary purified brine, and the mixture was reacted at 60℃ for 1.5 hours. After the reaction, the brine was filtered to obtain the secondary purified brine. At this point, all impurities such as aluminum, iron, magnesium, manganese, and fluorine in the brine were removed, and the main residue was potassium (K). + ~7.1g / L, Ca 2+ ~1.9 g / L. The brine, after secondary impurity removal, was subjected to a three-stage impurity removal process using a 200 g / L sodium carbonate solution (50 mL). After reacting for 0.5 h, the mixture was filtered to obtain purified brine and magnesium-calcium slag. Testing revealed that impurities such as aluminum, iron, fluorine, and manganese in the purified brine were all below 5 mg / L, and impurities such as calcium and magnesium were below 15 mg / L. On a liquid basis, the lithium loss rate during impurity removal in this example was 4.9%.

[0065] 1.9 L of purified brine was concentrated by evaporation to a Li₂O concentration of approximately 25 g / L. A saturated sodium carbonate solution was prepared by adding 1.05 times the molar amount of lithium ions using a reverse addition method. The solution was then subjected to a precipitation reaction at 90 °C. After aging for 2 hours, the solution was washed twice with deionized water at 90 °C and dried to obtain 61.13 g of lithium carbonate product. The primary precipitation rate was 78.94%. The lithium carbonate composition was: Li₂O₃–98.73%, K–0.64%, Na–0.18%, Ca–0.006%, Mg–0.001%, Fe–0.003%, Al–0.006%, Mn–0.007%.

[0066] Excluding lithium in the lithium precipitation mother liquor, the lithium yield of this process is greater than 88% throughout the entire process.

[0067] Example 4

[0068] One lithium-bearing ore is lepidolite, with the chemical formula K{Li 2-x Al 1+x [Al 2x Si 4-2x O 10 The main chemical components of the compound are: Li₂O ~ 3.3%, Na₂O ~ 2.1%, Al₂O₃ ~ 21.8%, SiO₂ ~ 48.44%, Fe₂O₃ ~ 0.18%, K₂O ~ 6.7%, CaO ~ 0.8%, and MgO ~ 0.23%.

[0069] Take 1.2 kg of lithium ore, 25 g of calcium fluoride, and 15 g of potassium sulfate, and add them sequentially to 2.2 L of 25% sulfuric acid. Heat in a water bath to 85°C, stirring at 200 r / min, and react for 2 hours. After the reaction is complete, filter and wash with water; the volume of the brine is measured to be 2.4 L, and its composition is K. + ~9.72g / L, Li2O ~15.49g / L, Al 3+ ~31.9 g / L, Fe 2+ ~1.18g / L, Ca 2+ ~0.40 / L, Mg 2+ ~0.37g / L, Mn 2+ ~0.39g / L, F - ~6.1 g / L. On a liquid basis, the lithium leaching rate of this lepidolite is 93.9%.

[0070] Take 2.0 L of lithium-extraction brine obtained from lithium mica acidification, adjust its pH to 2.0 with potassium hydroxide, add 110 g of potassium sulfate, and stir at 60℃ for 25 min. Then place it in a refrigeration unit, adjust the temperature to 5℃, and stir slowly for 40 min to obtain alum and 1.9 L of de-alumened brine. Lithium is essentially not lost in this process, and the main component of the de-alumened brine is potassium (K).+ ~8.2g / L, Li2O ~15.90g / L, Al 3+ ~7.9 g / L, Fe 3+ ~1.22g / L, Ca 2+ ~0.42 g / L, Mg 2+ ~0.39g / L, Mn 2+ ~0.42g / L, F - ~6.4g / L.

[0071] 75g of sodium phosphate was added to the de-alumated brine. After the sodium phosphate was fully dissolved, the pH of the aqueous leaching solution was adjusted to 4.5 using caustic soda flakes. The reaction temperature was 85℃, and the reaction time was 1.0 h. After standing and filtration, primary impurity-removed brine and aluminum fluoride residue were obtained. The main component of the primary impurity-removed brine was potassium (K). + ~8.1g / L, Li2O ~15.79g / L, Al 3+ ~0.28g / L, Fe 3+ ~ND, Ca 2+ ~0.32g / L, Mg 2+ ~0.34g / L, Mn 2+ ~0.35g / L, F - ~0.21g / L.

[0072] 80g of quicklime was added to the primary purified brine, and the mixture was reacted at 60℃ for 1.5 hours. After the reaction, the brine was filtered to obtain the secondary purified brine. At this point, all impurities such as aluminum, iron, magnesium, manganese, and fluorine in the brine were removed, and the main residue was potassium (K). + ~7.9g / L, Ca 2+ ~2.0 g / L. The brine, after secondary impurity removal, was subjected to a three-stage impurity removal process using a 200 g / L sodium carbonate solution (55 mL added). After reacting for 0.5 h, the mixture was filtered to obtain purified brine and magnesium-calcium slag. Testing revealed that impurities such as aluminum, iron, fluorine, and manganese in the purified brine were all below 5 mg / L, and impurities such as calcium and magnesium were below 15 mg / L. On a liquid basis, the lithium loss rate during impurity removal in this example was 5.3%.

[0073] 1.9 L of purified brine was concentrated by evaporation to a Li₂O concentration of approximately 25 g / L. A saturated sodium carbonate solution was prepared by adding 1.2 times the molar amount of lithium ions using a reverse addition method. The solution was then subjected to a precipitation reaction at 90 °C. After aging for 2 hours, the solution was washed twice with deionized water at 90 °C and dried to obtain 58.68 g of lithium carbonate product. The primary precipitation rate was 81.04%. The lithium carbonate composition was: Li₂O₃–98.53%, K–0.69%, Na–0.20%, Ca–0.007%, Mg–0.002%, Fe–0.004%, Al–0.005%, Mn–0.005%.

[0074] Excluding lithium in the lithium precipitation mother liquor, the lithium yield of this process is greater than 88% throughout the entire process.

[0075] Example 5

[0076] One lithium-bearing ore is lepidolite, with the chemical formula K{Li 2-x Al 1+x [Al 2x Si 4-2x O 10 The main chemical components of the compound are: Li₂O ~ 3.3%, Na₂O ~ 2.1%, Al₂O₃ ~ 21.8%, SiO₂ ~ 48.44%, Fe₂O₃ ~ 0.18%, K₂O ~ 6.7%, CaO ~ 0.8%, and MgO ~ 0.23%.

[0077] Take 1.2 kg of lithium ore, 70 g of alumina slag, 10 g of calcium fluoride, and 30 g of potassium sulfate, and add them sequentially to 2.2 L of 30% sulfuric acid. Heat in a water bath to 95°C, stirring at 300 r / min, and react for 6 h. After the reaction is complete, filter and wash with water; the volume of the brine is measured to be 2.4 L, and its composition is K. + ~18.4g / L, Li2O ~16.4g / L, Al 3+ ~39.2 g / L, Fe 2+ ~1.3g / L, Ca 2+ ~0.48 g / L, Mg 2+ ~0.35g / L, Mn 2+ ~0.45g / L, F - ~10.3 g / L. On a liquid basis, the lithium leaching rate of lepidolite is 99.4%.

[0078] Take 2.0 L of lithium-extraction brine obtained from lithium mica acidification, adjust its pH to 2.0 using potassium hydroxide, add 100 g of potassium sulfate, and stir at 60°C for 20 min. Then place it in a refrigeration unit, adjust the temperature to 5°C, and stir slowly for 30 min to obtain alum and 1.9 L of de-alumened brine. Lithium is essentially not lost in this process, and the main component of the de-alumened brine is potassium (K). + ~8.5g / L, Li2O ~17.23g / L, Al 3+ ~13.04 g / L, Fe 3+ ~1.38g / L, Ca 2+ ~0.52g / L, Mg 2+ ~0.41g / L, Mn 2+ ~0.49g / L, F - ~10.57g / L.

[0079] Add 95g of sodium phosphate to the alum-removing brine. After the sodium phosphate is fully dissolved, adjust the pH of the aqueous leaching solution to 4.5 using caustic soda flakes. The reaction temperature is 85℃, and the reaction time is 1.0 h. After settling and filtration, primary impurity-removed brine and aluminum fluoride slag are obtained. The main component of the primary impurity-removed brine is potassium (K). + ~8.4g / L, Li2O ~17.09g / L, Al 3+ ~0.41g / L, Fe 3+ ~ND, Ca 2+ ~0.33g / L, Mg 2+ ~0.35g / L, Mn 2+ ~0.40g / L, F - ~0.31g / L.

[0080] 100g of quicklime was added to the primary purified brine, and the mixture was reacted at 60℃ for 1.5 hours. After the reaction, the brine was filtered to obtain the secondary purified brine. At this point, all impurities such as aluminum, iron, magnesium, manganese, and fluorine in the brine were removed, and the main residue was potassium (K). + ~8.3g / L, Ca 2+ ~2.0 g / L. The brine, after secondary impurity removal, was subjected to a three-stage impurity removal process using a 200 g / L sodium carbonate solution (55 mL added). After reacting for 0.5 h, the mixture was filtered to obtain purified brine and magnesium-calcium slag. Testing revealed that impurities such as aluminum, iron, fluorine, and manganese in the purified brine were all below 5 mg / L, and impurities such as calcium and magnesium were below 15 mg / L. On a liquid basis, the lithium loss rate during impurity removal in this example was 4.8%.

[0081] 1.9 L of purified brine was concentrated by evaporation to a Li₂O concentration of approximately 25 g / L. A saturated sodium carbonate solution was prepared, and 1.2 times the molar amount of lithium ions of sodium carbonate was added using a reverse addition method. The precipitation reaction was carried out at 90 °C. After aging for 2 hours, the solution was washed twice with deionized water at 90 °C and dried to obtain 65.17 g of lithium carbonate product. The primary precipitation rate was 81.3%, and the lithium carbonate composition was: Li₂O₃–98.68%, K–0.74%, Na–0.20%, Ca–0.0067%, Mg–0.0018%, Fe–0.0016%, Al–0.0048%, Mn–0.014%.

[0082] Excluding lithium in the lithium precipitation mother liquor, the lithium yield of this process is greater than 88% throughout the entire process.

[0083] Comparative Example 1

[0084] One lithium-bearing ore is lepidolite, with the chemical formula K{Li 2-x Al 1+x [Al 2x Si 4-2x O 10The main chemical components of the compound are: Li₂O ~ 3.3%, Na₂O ~ 2.1%, Al₂O₃ ~ 21.8%, SiO₂ ~ 48.44%, Fe₂O₃ ~ 0.18%, K₂O ~ 6.7%, CaO ~ 0.8%, and MgO ~ 0.23%.

[0085] 1.2 kg of the above-mentioned lithium ore was added to 2.2 L of 30% sulfuric acid, heated in a water bath to 95°C, and stirred at 300 r / min for 6 h. After the reaction was complete, the brine was filtered, washed with water, and the volume was measured to be 2.4 L, with the composition being K. + ~4.8g / L, Li2O ~12.3g / L, Al 3+ ~30.7g / L, Fe 2+ ~0.9g / L, Ca 2+ ~0.3g / L, Mg 2+ ~0.2g / L, Mn 2+ ~0.2g / L, F - ~1.5 g / L. On a liquid basis, the lithium leaching rate of lepidolite is 74.45%.

[0086] Take 2.0 L of lithium-extraction brine obtained from lithium mica acidification, adjust its pH to 2.0 using potassium hydroxide, add 100 g of potassium sulfate, and stir at 60°C for 20 min. Then place it in a refrigeration unit, adjust the temperature to 5°C, and stir slowly for 30 min to obtain alum and 1.9 L of de-alumened brine. Lithium is essentially not lost in this process, and the main component of the de-alumened brine is potassium (K). + ~6.4g / L, Li2O ~12.4g / L, Al 3+ ~3.8g / L, Fe 3+ ~0.95g / L, Ca 2+ ~0.31g / L, Mg 2+ ~0.25g / L, Mn 2+ ~0.24g / L, F - ~1.7g / L.

[0087] Add 35g of sodium phosphate to the alum-removing brine. After the sodium phosphate is fully dissolved, adjust the pH of the aqueous leaching solution to 4.5 using caustic soda flakes. The reaction temperature is 85℃, and the reaction time is 1.0 h. After settling and filtration, primary impurity-removed brine and aluminum fluoride residue are obtained. The main component of the primary impurity-removed brine is potassium (K). + ~6.3g / L, Li2O ~12.32g / L, Al 3+ ~0.11g / L, Fe 3+ ~ND, Ca 2+ ~0.13g / L, Mg 2+ ~0.15g / L, Mn 2+~0.20g / L, F - ~0.12g / L.

[0088] 70g of quicklime was added to the primary purified brine, and the mixture was reacted at 60℃ for 1.5 hours. After the reaction, the brine was filtered to obtain the secondary purified brine. At this point, all impurities such as aluminum, iron, magnesium, manganese, and fluorine in the brine were removed, and the main residue was potassium (K). + ~6.3g / L, Ca 2+ ~2.0 g / L. The brine, after secondary impurity removal, was subjected to a three-stage impurity removal process using a 200 g / L sodium carbonate solution (55 mL added). After reacting for 0.5 h, the mixture was filtered to obtain purified brine and magnesium-calcium slag. Testing revealed that impurities such as aluminum, iron, fluorine, and manganese in the purified brine were all below 5 mg / L, and impurities such as calcium and magnesium were below 15 mg / L. On a liquid basis, the lithium loss rate during impurity removal in this example was 5.5%.

[0089] 1.9 L of purified brine was concentrated by evaporation to a Li₂O concentration of approximately 25 g / L. A saturated sodium carbonate solution was prepared, and 1.2 times the molar amount of lithium ions of sodium carbonate was added using a reverse addition method. The precipitation reaction was carried out at 90 °C. After aging for 2 hours, the solution was washed twice with deionized water at 90 °C and dried to obtain 48.22 g of lithium carbonate product. The primary precipitation rate was 81.1%, and the lithium carbonate composition was: Li₂O₃–98.63%, K–0.71%, Na–0.22%, Ca–0.007%, Mg–0.002%, Fe–0.001%, Al–0.0045%, Mn–0.018%.

[0090] Excluding lithium in the lithium precipitation mother liquor, the lithium yield of this process is less than 75% for the entire process.

[0091] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for the production of lithium carbonate from lithium ore by wet process of lithium extraction, characterized by, Includes the following steps: S1. Atmospheric pressure acid leaching: Lithium ore, sulfuric acid, fluoride, and potassium salt are added to a reaction vessel, heated, stirred, and filtered to obtain silicon slag and brine; the amount of fluoride added is 0.1 to 1 times the total molar amount of aluminum in the lithium ore; the amount of potassium salt added is 0 to 10% of the weight of the lithium ore; the mass percentage concentration of the sulfuric acid is 5% to 50%; the solid-liquid ratio in the reaction vessel is 0.5 to 4:1; S2. Cooling and alum precipitation: Adjust the pH of the brine with alkali, add potassium salt, stir to react, cool, and filter to obtain alum and de-alumened brine; adjust the pH of the brine to 0-2 with alkali; the alkali is selected from potassium hydroxide and / or sodium hydroxide. S3, Primary Impurity Removal: Phosphate and alkali are added to the de-alumening brine, stirred and reacted, and filtered to obtain aluminum-fluoride slag and primary purified brine; the obtained aluminum-fluoride slag is returned to the lithium ore acid leaching process in S1; the phosphate is selected from one or more of sodium phosphate, potassium phosphate, ammonium phosphate, diammonium hydrogen phosphate, and calcium phosphate; the amount of phosphate used is 0.8 to 1.2 times the molar amount of aluminum in the de-alumening brine; the alkali is sodium hydroxide, and the pH of the system is adjusted to 3.0 to 4.5 by adding alkali; S4. Secondary purification: Lime is added to the primary purified brine and stirred to react, resulting in aluminum-calcium slag and secondary purified brine. S5. Three-stage purification: Sodium carbonate is added to the secondary purified brine and stirred to react, resulting in magnesium-calcium slag and tertiary purified brine. S6. Concentration and Lithium Precipitation: The brine that has been purified three times is concentrated, and a saturated sodium carbonate solution is added to carry out a lithium precipitation reaction to obtain lithium carbonate.

2. The process according to claim 1, characterized in that, In S1, the lithium ore is selected from one or more of lepidolite, lepidolite, lithium ceramic stone, and lithium aluminum phosphate. The fluoride is selected from one or more of sodium fluoride, calcium fluoride, potassium fluoride, aluminum fluoride, hydrogen fluoride, and fluorosilicic acid. The temperature of the stirring reaction is 30~100℃, the stirring speed is 100~600r / min, and the reaction time is 2~12h.

3. The process of claim 1, wherein, In S1, the potassium salt is one or more of potassium sulfate, potassium chloride, potassium nitrate, and potassium phosphate.

4. The process of claim 1, wherein, In S2, the potassium salt is selected from one or more of potassium sulfate, potassium chloride, potassium nitrate, and potassium phosphate; the potassium salt is added to adjust the potassium-aluminum molar ratio in the brine to 0.5~1.1:

1.

5. The process of claim 1, wherein, In S2, the mixture is stirred and reacted at 40~70℃ for 20~120 min, and then cooled to 0~10℃ for 20~80 min to crystallize.

6. The process according to claim 1, characterized in that, In S3, the temperature of the stirring reaction is 20~90℃, and the reaction time is 0.5~3h.

7. The process according to claim 1, characterized in that, In S4, the amount of the lime added is 30-100 kg / m3 of the volume of the once-purified brine 3 ; The temperature of the stirring reaction is 50~80℃, the reaction time is 0.5~3h, and the stirring speed is 100~600r / min.

8. The process according to claim 1, characterized in that, In step S5, the amount of sodium carbonate added is 1.0 to 1.2 times the molar amount of calcium in the secondary purified brine; the concentration of the sodium carbonate solution is 200 g / L to 300 g / L. The stirring reaction time is 0.5~3h, and the reaction temperature is 10~50℃.

9. The process according to claim 1, characterized in that, In step S6, the sodium carbonate is added in solution form, and the amount of sodium carbonate added is 1.0 to 1.5 times the molar amount of lithium in the three-stage purified brine based on the volume of the brine; the concentration of the sodium carbonate solution is 200 g / L to 300 g / L. The lithium precipitation reaction is carried out at a temperature of 80~100℃ and an aging time of 1~5h.

Images