Purification and anti-solubility production method of battery-grade lithium carbonate

Abstract

The application discloses a purification and dissolution-resisting production method of battery-grade lithium carbonate, which comprises the following steps: 1) primary purification: cooling and cold precipitation of a crude lithium sulfate solution to obtain a primary purified solution; 2) secondary purification: adjusting the pH with sodium hydroxide, adding a flocculating agent, and filtering to obtain a secondary purified solution; 3) tertiary purification: adjusting the pH with sulfuric acid, sequentially adding disodium ethylenediaminetetraacetate, oxalic acid and activated carbon, and filtering to obtain a tertiary purified solution; 4) carbonization and synthesis: determining the content of Li in the tertiary purified solution, adding solid Na2CO3 or Na2CO3 solution according to the content of Li, and reacting for 30 min; adding dodecyl primary amine and reacting for 30 min, and filtering to obtain crude lithium carbonate; 5) washing: washing twice with water, washing with ethanol, filtering and drying to obtain battery-grade lithium carbonate; and 6) mother liquor recovery. The battery-grade lithium carbonate produced has a purity higher than 99.95%, a yield higher than 99%, and a whiteness higher than 95%, and realizes safe and environment-friendly production with high purity, high yield and high whiteness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium carbonate preparation, and particularly relates to a purification and dissolution-resisting production method of battery-grade lithium carbonate. BACKGROUND

[0002] Lithium element is represented by Li, and the atomic weight is 6.941. The specific gravity of lithium at 0℃ is 0.534, which is the lightest metal known at present and can float on petroleum. Lithium salts can be considered to be derived from Li2O, including lithium chloride (LiCl), lithium sulfate (Li2SO4), lithium carbonate (Li2CO3), etc. The solubility of lithium carbonate (Li2CO3) is 13.1 g / L at 13℃, which is the main raw material of new energy storage lithium batteries.

[0003] With the continuous development of new energy, the demand for lithium carbonate is increasing. At present, the method for producing battery-grade lithium carbonate in China mainly adopts acid leaching to obtain lithium sulfate solution, and then reacts with soda (Na2CO3) to obtain the product. For example, patent application No. CN201310001733.2 discloses a clean production method of battery-grade lithium carbonate. Lithium spodumene is used as raw material, and battery-grade lithium carbonate is prepared through five steps of β-lithium spodumene lithium concentrate preparation, lithium sulfate solution preparation, ion removal, lithium carbonate preparation, and battery-grade lithium carbonate preparation. The production method of battery-grade lithium carbonate in the present application can produce products with stable quality, which meets the industry standards of battery-grade lithium carbonate, and has important industrial popularization value.

[0004] CN201610129932.5 discloses a method for producing high-purity battery-grade lithium carbonate from lithium sulfate solution, which includes the following steps: 1) lithium sulfate solution precipitation refining step: using lithium sulfate solution as raw material, first adding sodium hydroxide to precipitate sodium sulfate decahydrate and separate it out, and then using EDTA to complex calcium and magnesium impurities in the lithium solution after precipitation; 2) carbonization and lithium precipitation step: continuously carbonizing and precipitating lithium at a relatively constant high temperature to obtain high-purity battery-grade lithium carbonate product and lithium precipitation mother liquor; 3) mother liquor recovery step: the generated lithium precipitation mother liquor is neutralized with sulfuric acid and concentrated, and then returned to the lithium sulfate solution raw material for recycling. The battery-grade lithium carbonate produced by the method has high purity, and the treatment method of the lithium precipitation mother liquor makes the lithium carbonate produced from the recovered lithium sulfate solution still a high-purity battery-grade lithium carbonate product.

[0005] The above methods all use lithium sulfate and soda to prepare battery-grade lithium carbonate through double decomposition reaction, which mainly includes four steps of purification of lithium sulfate solution, carbonization and double decomposition synthesis, washing, and drying. Although the above method can prepare battery-grade lithium carbonate with high purity, there are still the following problems:

[0006] 1) In the carbonization metathesis synthesis step, liquid soda ash (Na2CO3 solution) and purified lithium sulfate solution are used for the metathesis reaction. However, the lithium content in the lithium sulfate solution is not taken into account. During the metathesis reaction, if the lithium content is too low, the chance of ion collision will be reduced, or if the lithium content is too high, the alkali will be difficult to dissolve, and the reaction will form a coating. Both of these will reduce the conversion rate of Li2CO3 and greatly reduce the yield of Li2CO3. In addition, Li2CO3 will also dissolve and be lost during the metathesis reaction, which will reduce the yield of Li2CO3.

[0007] 2) In the washing process, water is used for multiple washes, which can easily lead to the loss of the originally dispersed lithium, resulting in a low yield of Li2CO3.

[0008] 3) None of the above production methods involve research on the whiteness of battery-grade lithium carbonate. In the battery-grade lithium carbonate industry, whiteness has a significant impact on the quality of battery-grade lithium carbonate. During the production process of battery-grade lithium carbonate, some organic pigments are not effectively removed, which not only reduces the purity of battery-grade lithium carbonate but also leads to a decrease in its whiteness, seriously affecting the conductivity of downstream products. Furthermore, when the whiteness is <92%, it is considered unqualified; when the whiteness is between 92-95%, it is considered qualified; and when the whiteness is ≥95%, it is considered superior. However, after preparing battery-grade lithium carbonate using the above methods and testing the whiteness of the lithium carbonate, it was found that the whiteness of the lithium carbonate prepared by both methods was below 80%. The whiteness of battery-grade lithium carbonate prepared using the above methods cannot meet the requirements, making it difficult to meet quality requirements and market demands. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a purification and solvent-inhibiting production method for battery-grade lithium carbonate. This method is simple, low-cost, and can greatly improve the purity and yield of battery-grade lithium carbonate.

[0010] The technical solution adopted by this invention to solve its technical problem is: a method for producing battery-grade lithium carbonate with purification and solvent inhibition, comprising the following steps:

[0011] 1) Primary purification: The crude lithium sulfate solution is cooled and precipitated to allow sodium sulfate decahydrate to precipitate. The sodium sulfate is then removed by solid-liquid separation to obtain the primary purified solution.

[0012] 2) Secondary purification: The primary purified liquid is heated to 40℃, the pH of the solution is adjusted with sodium hydroxide, impurities are precipitated in stages, flocculant is added and the solution is allowed to stand, filtered and the filtrate is collected to obtain the secondary purified liquid.

[0013] 3) tertiary purification: the secondary purification solution is warmed to 40℃, sulfuric acid is used to adjust the pH of the solution to 6.5-7, ethylenediaminetetraacetic acid disodium salt and oxalic acid are first added, then activated carbon is added to remove organic pigments, filtration is performed, the filtrate is warmed to 90-95℃, and the solution is kept at this temperature for 30 min, the supernatant is observed, and the filtrate is collected after filtration to obtain a tertiary purification solution;

[0014] 4) carbon synthesis: the content of Li in the tertiary purification solution is determined, and solid Na2CO3 or Na2CO3 solution is slowly added to the tertiary purification solution at a temperature of 90℃ until the pH of the solution is 9, and the solution is kept at this temperature for 30 min; then dodecyl primary amine is added, and the reaction is carried out at 90℃ for 30 min, and the obtained filter cake is crude lithium carbonate;

[0015] 5) washing: the crude lithium carbonate is first washed twice with water, filtered, and then washed a third time with ethanol, and dried after filtration to obtain battery-grade lithium carbonate;

[0016] 6) mother liquor recovery: the filtrate after filtration in step 4) and the filtrate after filtration in step 5) are combined to obtain a mother liquor which is recovered for use.

[0017] In the above purification and dissolution-resistant production method of battery-grade lithium carbonate, step 1) uses the method of cooling and cold separation of crude lithium sulfate solution to remove sodium sulfate crystals, which can reduce the water content and volume of the solution, increase the concentration of lithium sulfate, and improve the conversion rate of lithium carbonate;

[0018] Step 2) uses sodium hydroxide to adjust the pH, and at different pH ranges, trace amounts of Fe, Ni, Co, Ca, Mg, Pb, Zn, Cu, etc. in the solution are precipitated as hydroxyl flocculation, and then a flocculating agent is added to increase the flocculation and further remove impurities. At the same time, by controlling the temperature to be 40℃, at this temperature, except for NaOH, other hydroxides will not appear the phenomenon of reverse dissolution, which not only greatly improves the speed of subsequent filtration, but also ensures the effective removal of impurities and avoids the residue of impurities, thereby improving the purity of the prepared lithium carbonate;

[0019] Step 3) first uses sulfuric acid to adjust the pH to eliminate hydroxyl groups and convert calcium into calcium sulfate to remove it, then adds ethylenediaminetetraacetic acid disodium salt to separate the remaining heavy metals in the solution, and then adds oxalic acid to precipitate and remove the heavy metals as insoluble oxalate; then activated carbon is added to adsorb organic pigments, which can greatly improve the whiteness of the prepared lithium carbonate;

[0020] Step 4) The lithium sulfate is subjected to a double decomposition reaction with soda ash by using reinforced Na2CO3 or Na2CO3 solution, in which, by adding dodecyl primary amine, the nucleophilic and catalytic performance of the high carbon molecule is used to promote the growth and thickening of Li2CO3 crystal nucleus, the crystallization is uniform, the dehydration is fast, the Li2CO3 is hardly soluble in water, and the dissolution of Li2CO3 in the solution is prevented. Meanwhile, the dodecyl primary amine has the feature of being soluble at 27℃, which is convenient for washing and does not cause the phenomenon of solvent residue, and can reduce the loss of Li2CO3 caused by the dissolution of Li2CO3 in the solution, thereby greatly improving the yield of Li2CO3. In addition, the dodecyl primary amine is an alkaline high carbon compound and is completely dissolved above 27℃, and can take some organic pigments away with the solution, thereby further improving the whiteness of the lithium carbonate and making the whiteness of the prepared lithium carbonate meet the production requirements.

[0021] In step 5), the impurities attached to the crude lithium carbonate are removed by twice water washing, and then the residual organic matter (such as organic sulfur, phosphorus, boron and the like) is washed away by using ethanol, which not only can reduce the content of impurities in the produced lithium carbonate and further improve the whiteness of the produced lithium carbonate, but also can prevent the dissolution of Li2CO3 by using the ethanol washing method, effectively reduce the loss of Li2CO3 in the washing process, and improve the yield of Li2CO3.

[0022] In step 6), the filtrate after the filtration in the carbonization synthesis step and the filtrate after the filtration in the washing step both contain residual lithium, in order to recycle the lithium and meet the environmental protection requirements, the filtrates are collected and recycled, which can further improve the yield of lithium carbonate.

[0023] Further, the temperature during the cooling and precipitation in step 1) is 3-5℃, and the cooling and precipitation time is 4-6h.

[0024] Further, the specific operation steps of the staged precipitation of impurities in step 2) are as follows: when the pH of the solution is adjusted to 7.5-8, the addition of sodium hydroxide is stopped, and iron and cobalt are converted into Fe(OH)3 and Co(OH)2 respectively, after 10-20min of precipitation, the pH of the solution is continuously adjusted to 10-11 by adding sodium hydroxide, the addition of sodium hydroxide is stopped, and nickel and copper are converted into (Ni(OH)2 and Cu(OH)2 respectively, after 10-20min of precipitation, the pH of the solution is continuously adjusted to 12-14 by adding sodium hydroxide, and calcium and magnesium are converted into (Ca(OH)2 and Mg(OH)2 respectively, and the precipitation time is 10-30min.

[0025] Further, the amount of ethylenediaminetetraacetic acid disodium and oxalic acid used in step 3) is 2-3g / L, and the amount of activated carbon used is 10-20g / L.

[0026] Further, the standard for adding solid Na2CO3 or Na2CO3 solution to the third purification liquid in step 4) is: when the content of Li is less than 8 g / L, add solid Na2CO3; when the content of Li is higher than 15 g / L, add Na2CO3 solution with a concentration of 30-40%.

[0027] In the above scheme, when the content of Li is less than 8 g / L, if the method of adding Na2CO3 solution is adopted, the water content in the solution will be increased, the concentration of Li will be lower, the collision opportunity between ions will be greatly reduced, and thus the conversion rate of Li2CO3 will be reduced, and the yield of Li2CO3 will be reduced. In order to effectively promote the double decomposition reaction, the method of adding solid Na2CO3 can increase the conversion rate of Li2CO3, and thus improve the yield of Li2CO3.

[0028] When the content of Li is 8-15 g / L, the concentration of the solution is slightly high, and if solid Na2CO3 is added, a small part of Na2CO3 will be difficult to dissolve, which will reduce the conversion effect of Li2CO3, and thus the yield of Li2CO3 will be reduced.

[0029] When the content of Li is higher than 15 g / L, the concentration of the solution is relatively high, and if solid Na2CO3 is added, it will be difficult for Na2CO3 to dissolve, and a surface will be formed. Excessive reaction generates insoluble Li2CO3 to form a package, and the utilization of Na2CO3 is reduced, and the conversion effect of Li2CO3 is also reduced, and thus the yield of Li2CO3 will be reduced.

[0030] Further, the amount of dodecyl primary amine used is 2-3 g / L.

[0031] Further, when adding solid Na2CO3 or Na2CO3 solution to the third purification liquid in step 4), the temperature of the solution should be controlled at 90°C, and the addition should be carried out in multiple times, and at the same time, the change of pH of the solution should be detected at any time; when the pH is 12, stop adding pure alkali; when the pH drops to 8, it indicates that the carbonization is not complete, and the pure alkali should be slowly added to adjust the pH; when the pH is 9, stop, which indicates that the amount of alkali has been enough, and the addition of pure alkali should be stopped, and after 30 min of heat preservation reaction, dodecyl primary amine is added.

[0032] Further, the specific operation steps of the washing in step 5) are as follows: once washing is performed by adding water with a temperature of 40℃ to the crude lithium carbonate at a solid-liquid ratio of 1:4, and after washing for 30-40 min, filtration is performed; twice washing is performed by adding water to the crude lithium carbonate obtained after the once washing and filtration at a solid-liquid ratio of 1:4 at a temperature of 55-60℃, and after washing for 30-40 min, filtration is performed; and thrice washing is performed by adding ethanol with a concentration of 40% to the crude lithium carbonate obtained after the twice washing and filtration at a solid-liquid ratio of 1:4 at a temperature of 60-90℃, and after washing for 30-40 min, filtration is performed, the filtered material is detected for the content of sulfate and calcium, if the content of sulfate and calcium meets the standard, the filtered material is directly dried at 70-80℃ for 4-6 h, and the content of lithium carbonate in the dried product is determined; if the content of lithium carbonate is ≥99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained.

[0033] Further, if the content of sulfate and calcium in the filtered material does not meet the standard, water is added at a solid-liquid ratio of 1:1, and CO2 gas is dissolved, after complete dissolution, the temperature is increased to 90℃, and after keeping the temperature for 30-40 min, when the pH is increased to 9, lithium carbonate is re-precipitated, after keeping the temperature at 90℃ for 30-40 min, filtration is performed, and the filtered material is dried at 70-80℃ for 4-6 h; if the content of lithium carbonate is greater than 99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained. In this step, by detecting the content of sulfate and calcium in the filtered material, it can be ensured that the content of sulfate and calcium in the produced lithium carbonate meets the national standard, and by adding water and CO2 to the filtered material that does not meet the standard, the residual sulfate and calcium in the filtered material can be further washed away, and lithium carbonate can be re-precipitated, which can improve the purity and yield of the produced lithium carbonate.

[0034] Further, if the content of lithium carbonate in the dried product determined is <99.5%, cokesol treatment is still needed, the specific operation steps of the cokesol treatment are as follows: water is added to the dried product at a solid-liquid ratio of 1:3 at a temperature of 90℃ for washing for 30-50 min, filtration is performed, and the filtered material is dried at 70-80℃ for 4-5 h, and battery-grade lithium carbonate is obtained. In this step, the unqualified dried product is treated by cokesol treatment, because: during the drying and dehydration and decarburization process, OH - salts are difficult to be dried and removed, and the effect of water-soluble is the best, therefore, the method of washing the unqualified dried product with water again is selected to remove OH - salts (such as NaOH, etc.), and the purity of the produced lithium carbonate is further improved.

[0035] Further, the specific operation steps of step 6) are as follows: the mother liquor obtained by combining the filtrate after filtration in step 4) and the filtrate after filtration in step 5) is frozen at a temperature of 0-5°C for 4h, so that sodium sulfate decahydrate and sodium carbonate decahydrate are precipitated out, then the mother liquor is evaporated until white lithium carbonate is precipitated, and after cooling to 60°C, filtration is performed, and the filtered material is returned to step 5) for washing, and the filtrate is returned to step 1) for recycling.

[0036] The battery-grade lithium carbonate purification and dissolution-preventing production method has the following advantages:

[0037] (1) In the purification process of the crude lithium sulfate solution, the addition of activated carbon can effectively adsorb organic pigments in the solution, greatly improving the whiteness of the produced battery-grade lithium carbonate;

[0038] (2) In the carbonization synthesis step, different forms of soda ash (solid Na2CO3 or liquid Na2CO3) are selected according to the content of Li and added to the purified lithium sulfate solution for double decomposition reaction, which can effectively increase the collision opportunity between ions in the solution, avoid the phenomenon of difficult dissolution of alkali, effectively promote the occurrence of double decomposition reaction, improve the conversion rate of Li2CO3, and further effectively improve the yield of Li2CO3; and in this step, the addition of dodecyl primary amine not only effectively prevents the dissolution of Li2CO3 in the solution, further improves the yield of Li2CO3, but also improves the whiteness of Li2CO3, thereby improving the quality of the produced lithium carbonate, and the whiteness and purity of the produced battery-grade lithium carbonate meet the market demand;

[0039] (3) In the washing step, ethanol is used for the third washing, which not only can wash away the residual organic matter and reduce the impurity content in the produced lithium carbonate, but also can prevent the dissolution of Li2CO3, effectively reduce the loss of Li2CO3 during the washing process, and improve the yield of Li2CO3;

[0040] (4) By detecting the content of sulfate and calcium in the filtered material after washing, it can be ensured that the content of sulfate and calcium in the produced lithium carbonate meets the national standard, and by adding water and CO2 to the filtered material that does not meet the standard, the residual sulfate and calcium in the filtered material can be further washed away, and lithium carbonate can be re-precipitated, which can improve the purity and yield of the produced lithium carbonate;

[0041] (5) By detecting the content of Li2CO3 in the dry product prepared in step 5), the dry product that does not meet the standard is treated by pyrosol, and OH- salt (such as NaOH, etc.) is further removed by water washing, which can greatly improve the purity of the produced lithium carbonate;

[0042] (6) The production process is simple and low in cost. Under the synergistic cooperation, mutual action and mutual influence of various operation steps, the purity of the battery-grade lithium carbonate produced reaches more than 99.95%, the yield (calculated according to lithium element) is higher than 99%, and the whiteness is higher than 95%, realizing the safe and environmentally-friendly production of battery-grade lithium carbonate with high purity, high yield and high whiteness, and greatly improving the quality of the battery-grade lithium carbonate. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A process flow chart of the purification and dissolution-resisting production method of the battery-grade lithium carbonate;

[0044] Figure 2 Influence of different dodecyl primary amine addition amounts on the whiteness of the battery-grade lithium carbonate;

[0045] Figure 3 Influence of different dodecyl primary amine addition amounts on the yield of the battery-grade lithium carbonate. DETAILED DESCRIPTION

[0046] The application will be further described below in combination with the drawings and examples, but these specific implementation solutions do not limit the protection scope of the application in any way.

[0047] Example 1

[0048] A purification and dissolution-resisting production method of battery-grade lithium carbonate, a process flow chart thereof is shown as Figure 1 The specific steps include the following:

[0049] 1) Primary purification: 15000L of a crude lithium sulfate solution with a lithium concentration of 6g / L is cooled to 4℃, and is cold-analyzed for 5h, so that sodium sulfate decahydrate (Na2SO4·10H2O) is precipitated and removed by centrifugal separation, and the centrifugal liquid is collected to obtain a primary purification liquid;

[0050] 2) Secondary purification: the primary purification liquid is warmed to 40℃, and a sodium hydroxide solution with a concentration of 40% is used to adjust the pH of the solution, and the impurities are precipitated in stages, wherein when the pH of the solution is adjusted to 7.5-8, the addition of sodium hydroxide is stopped, so that iron and cobalt are respectively converted into Fe(OH)3 and Co(OH)2, after 15min of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 10-11, and the addition of sodium hydroxide is stopped, so that nickel and copper are respectively converted into (Ni(OH)2 and Cu(OH)2, after 15min of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 12-14, and the addition of sodium hydroxide is stopped, so that calcium and magnesium are respectively converted into (Ca(OH)2 and Mg(OH)2, and the precipitation time is 20min; then 1000mL / m 3After adding polyacrylamide (0.5 g of polyacrylamide is dissolved in 300 ml of water to prepare) and standing for 20 min, the solid is removed by filtration, and the filtrate is collected to obtain the secondary purification liquid;

[0051] 3) tertiary purification: the secondary purification liquid is warmed to 40℃, and dilute sulfuric acid is used to adjust the pH of the solution to 6.5-7. After stirring, 2.5 g / L of disodium ethylenediaminetetraacetate is added, 15 min later, 2.5 g / L of oxalic acid is added, 30 min later, 15 g / L of activated carbon is added to remove organic pigments, 30 min later, the solution is filtered, then the filtrate is warmed to 95℃, and kept for 30 min. The supernatant is observed, and the filtrate is collected after filtration to obtain the tertiary purification liquid;

[0052] 4) carbonization synthesis: the content of Li (also referred to as the concentration of Li, in g / L) in the tertiary purification liquid is determined. The content of Li is 7 g / L, and solid Na2CO3 is slowly added to the tertiary purification liquid at a dosage of 5.1 g / L. When adding the solid Na2CO3, the temperature of the solution should be controlled at 90℃, and the solution pH should be detected at any time. When the pH is 12, the addition of the solid Na2CO3 is stopped. When the pH drops to 8, it indicates that the carbonization is not complete, and the solid Na2CO3 should be slowly added to adjust the pH. When the pH is 9, the addition of the solid Na2CO3 is stopped. After keeping the solution at 90℃ for 30 min, 3 g / L of dodecyl primary amine (dodecyl primary amine is dissolved and diluted with anhydrous ethanol at 30℃ to prepare, with a concentration of 0.5 g / 100 ml) is added, and the solution is reacted at 90℃ for 30 min. After filtration, the obtained filter cake is the crude lithium carbonate;

[0053] 5) washing: first, add water to the crude lithium carbonate at a solid-liquid ratio of 1:4 and a temperature of 40°C for primary washing, as the solubility of Na2SO4 and Na2CO3 is the largest at 40°C, filter after washing for 35 min; then add water to the crude lithium carbonate obtained after primary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 60°C for secondary washing, filter after washing for 35 min; then add ethanol with a concentration of 40% to the crude lithium carbonate obtained after secondary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 80°C for tertiary washing, filter after washing for 35 min, and detect the contents of sulfate and calcium in the filtered material, if the contents of sulfate and calcium meet the standards (the content of sulfate is <0.08%, and the content of calcium is <0.005%), directly dry the filtered material at 75°C for 5 h, and detect the content of lithium carbonate in the dried product; if the content of lithium carbonate is 99.98% ≥ 99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained; and the contents of Na, Mg, Ca, K, Fe, Zn, Cu, Pb, Si, Al, Mn, Ni, SO4, and Cl in the prepared battery-grade lithium carbonate are <0.025%, <0.008%, <0.005, <0.001, <0.001, <0.0003, <0.0003, <0.0003, <0.003, <0.001, <0.0003, <0.001, <0.08, and <0.003, respectively, meeting the standards of YS / T 582-2013 Battery-Grade Lithium Carbonate; 2- - 5) washing: first, add water to the crude lithium carbonate at a solid-liquid ratio of 1:4 and a temperature of 40°C for primary washing, as the solubility of Na2SO4 and Na2CO3 is the largest at 40°C, filter after washing for 35 min; then add water to the crude lithium carbonate obtained after primary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 60°C for secondary washing, filter after washing for 35 min; then add ethanol with a concentration of 40% to the crude lithium carbonate obtained after secondary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 80°C for tertiary washing, filter after washing for 35 min, and detect the contents of sulfate and calcium in the filtered material, if the contents of sulfate and calcium meet the standards (the content of sulfate is <0.08%, and the content of calcium is <0.005%), directly dry the filtered material at 75°C for 5 h, and detect the content of lithium carbonate in the dried product; if the content of lithium carbonate is 99.98% ≥ 99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained; and the contents of Na, Mg, Ca, K, Fe, Zn, Cu, Pb, Si, Al, Mn, Ni, SO4, and Cl in the prepared battery-grade lithium carbonate are <0.025%, <0.008%, <0.005, <0.001, <0.001, <0.0003, <0.0003, <0.0003, <0.003, <0.001, <0.0003, <0.001, <0.08, and <0.003, respectively, meeting the standards of YS / T 582-2013 Battery-Grade Lithium Carbonate;

[0054] 6) mother liquor recovery: freeze the mother liquor obtained by combining the filtrate after filtration in step 4) and the filtrate after filtration in step 5) at a temperature of 3°C for 4 h, so that sodium sulfate decahydrate and sodium carbonate decahydrate are precipitated, evaporate the mother liquor until white lithium carbonate is precipitated, cool to 60°C, and filter, and return the filtered material to step 5) for washing, and return the filtrate to step 1) for recycling.

[0055] Example 2

[0056] A purification and dissolution-resistant production method of battery-grade lithium carbonate, comprising the following steps:

[0057] 1) primary purification: cool 15000 L of crude lithium sulfate solution with a lithium concentration of 12 g / L to 5°C, and precipitate sodium sulfate decahydrate (Na2SO4·10H2O) after 6 h of cold precipitation, and remove it by centrifugal separation, collect the centrifugal liquid, and obtain a primary purification liquid;

[0058] ​2) Secondary purification: the primary purified solution is warmed to 40°C, the pH of the solution is adjusted using a 40% sodium hydroxide solution, and the impurities are precipitated in stages. When the pH of the solution is adjusted to 7.5-8, the addition of sodium hydroxide is stopped, and iron and cobalt are converted into Fe(OH)3 and Co(OH)2, respectively. After 20 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 10-11, and the addition of sodium hydroxide is stopped, and nickel and copper are converted into (Ni(OH)2 and Cu(OH)2, respectively. After 10-20 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 12-14, and calcium and magnesium are converted into (Ca(OH)2 and Mg(OH)2, respectively. After 30 minutes of precipitation, 1000 mL of the secondary purified solution is prepared for every 1 kg of lithium carbonate, and the solution is filtered. 3 After the addition of polyacrylamide (0.5 g of polyacrylamide is dissolved in 300 mL of water to prepare), the solution is allowed to stand for 30 minutes, and the solid is removed by filtration. The filtrate is collected to obtain the secondary purified solution.

[0059] 3) Tertiary purification: the secondary purified solution is warmed to 40°C, the pH of the solution is adjusted to 6.5-7 using dilute sulfuric acid, and the solution is stirred. Then, 3 g / L of disodium ethylenediaminetetraacetate is added, followed by the addition of 3 g / L of oxalic acid after 20 minutes. After 30 minutes, 20 g / L of activated carbon is added to remove organic pigments. After 30 minutes, the solution is filtered, and the filtrate is warmed to 95°C and maintained for 30 minutes. The supernatant is observed, and the clear solution is filtered to obtain the tertiary purified solution.

[0060] 4) Carbon synthesis: the content of Li (also referred to as the concentration of Li, in g / L) in the tertiary purified solution is determined. The content of Li is 13 g / L, and 9.5 g / L of Na2CO3 solution with a concentration of 40% is slowly added to the tertiary purified solution. When adding the pure alkali, the temperature of the solution should be controlled at 90°C, and the pH of the solution should be monitored at all times. When the pH is 12, the addition of pure alkali is stopped. When the pH drops to 8, it indicates that the carbonization is not complete, and the addition of pure alkali should be slow to adjust the pH. When the pH is 9, the addition of pure alkali should be stopped. After 30 minutes of reaction, 2 g / L of dodecyl primary amine (dodecyl primary amine is dissolved and diluted with anhydrous ethanol at 30°C to prepare a solution with a concentration of 0.5 g / 100 mL) is added. The reaction is carried out at 90°C for 30 minutes, and the filter cake obtained is crude lithium carbonate.

[0061] 5) washing: first, add water to the crude lithium carbonate at a solid-liquid ratio of 1:4 and a temperature of 40°C for primary washing, as the solubility of Na2SO4 and Na2CO3 is the largest at 40°C, filter after washing for 40 min; then add water to the crude lithium carbonate obtained after primary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 60°C for secondary washing, filter after washing for 40 min; then add ethanol with a concentration of 40% to the crude lithium carbonate obtained after secondary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 90°C for tertiary washing, filter after washing for 40 min, and detect the contents of sulfate and calcium in the filtered material, if the contents of sulfate and calcium meet the standards (the content of sulfate is <0.08%, and the content of calcium is <0.005%), directly dry the filtered material at 80°C for 6 h, and detect the content of lithium carbonate in the dried product; if the content of lithium carbonate (i.e., the purity of lithium carbonate) is 99.97% ≥ 99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained; and the battery-grade lithium carbonate prepared has a content of Na <0.025%, a content of Mg <0.008%, a content of Ca <0.005, a content of K <0.001, a content of Fe <0.001, a content of Zn <0.0003, a content of Cu <0.0003, a content of Pb <0.0003, a content of Si <0.003, a content of Al <0.001, a content of Mn <0.0003, a content of Ni <0.001, a content of SO4 <0.08, a content of Cl <0.003, which meets the standard of YS / T 582-2013 Battery-Grade Lithium Carbonate; 2- -

[0062] 6) mother liquor recovery: freeze the mother liquor obtained by combining the filtrate after filtration in step 4) and the filtrate after filtration in step 5) at a temperature of 5°C for 4 h, so that sodium sulfate decahydrate and sodium carbonate decahydrate are precipitated, evaporate the mother liquor until white lithium carbonate is precipitated, filter after cooling to 60°C, return the filtered material to step 5) for washing, and return the filtrate to step 1) for recycling.

[0063] Example 3

[0064] A purification and dissolution-preventing production method of battery-grade lithium carbonate, comprising the following steps:

[0065] 1) primary purification: cool 15000 L of crude lithium sulfate solution with a lithium concentration of 20 g / L to 3°C, precipitate sodium sulfate decahydrate (Na2SO4·10H2O) for 4 h, and remove it by centrifugal separation, collect the centrifugal liquid, and obtain a primary purification liquid;

[0066] ​​2) Secondary purification: the primary purified solution is warmed to 40°C, the pH of the solution is adjusted using a 40% sodium hydroxide solution, and the impurities are precipitated in stages. When the pH of the solution is adjusted to 7.5-8, the addition of sodium hydroxide is stopped, and iron and cobalt are converted into Fe(OH)3 and Co(OH)2, respectively. After 10 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 10-11, and the addition of sodium hydroxide is stopped to convert nickel and copper into (Ni(OH)2 and Cu(OH)2, respectively. After 10 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 12-14, and calcium and magnesium are converted into (Ca(OH)2 and Mg(OH)2, respectively. After 10 minutes of precipitation, the solution is filtered, and the filtrate is collected to obtain the secondary purified solution. 3 After 10 minutes of standing, the solid is removed by filtration, and the filtrate is collected to obtain the secondary purified solution.

[0067] 3) Tertiary purification: the secondary purified solution is warmed to 40°C, the pH of the solution is adjusted to 6.5-7 using dilute sulfuric acid, and the solution is stirred. Then, 2 g / L of disodium ethylenediaminetetraacetate is added, followed by 2 g / L of oxalic acid after 10 minutes. After 30 minutes, 10 g / L of activated carbon is added to remove organic pigments. After 30 minutes, the solution is filtered, and the filtrate is warmed to 95°C and kept at this temperature for 30 minutes. The supernatant is clear and transparent, and the filtrate is collected to obtain the tertiary purified solution.

[0068] 4) Carbon synthesis: the content of Li (also referred to as the concentration of Li, in g / L) in the tertiary purified solution is measured. The content of Li is determined to be 21 g / L, and 40% Na2CO3 solution is slowly added to the tertiary purified solution at a rate of 15.4 g / L. When adding the pure alkali, the temperature of the solution should be controlled at 90°C, and the pH of the solution should be monitored at all times. When the pH is 12, the addition of pure alkali is stopped. When the pH drops to 8, it indicates that the carbonization is not complete, and the addition of pure alkali should be adjusted. When the pH is 9, the addition of pure alkali should be stopped. After 30 minutes of reaction, 2.5 g / L of dodecyl primary amine (dodecyl primary amine is dissolved and diluted in anhydrous ethanol at 30°C to prepare a solution with a concentration of 0.5 g / 100 mL) is added, and the reaction is carried out at 90°C for 30 minutes. The filter cake obtained is crude lithium carbonate.

[0069] 5) Washing: First, add water at 40℃ to the crude lithium carbonate at a solid-liquid ratio of 1:4 for a first wash. Na₂SO₄ and Na₂CO₃ have the highest solubility at 40℃. After washing for 30 minutes, filter. Then, add water to the crude lithium carbonate obtained after the first wash and filtration at a solid-liquid ratio of 1:4 and wash a second time at 60℃ for 30 minutes, followed by filtration. Finally, add 40% ethanol to the crude lithium carbonate obtained after the second wash and filtration at a solid-liquid ratio of 1:4 and wash a third time at 90℃ for 30 minutes, followed by filtration. Analyze the sulfate and calcium content of the filtered material. The results show that the sulfate and calcium content meet the standards (sulfate content < 0.08%, calcium content < 0.005%). The filtered material is then directly dried at 80℃ for 6 hours, and the lithium carbonate content in the dried product is determined. If the lithium carbonate content (i.e., the purity of lithium carbonate) is 99.96% ≥ 99.5%, the dried product is qualified, yielding battery-grade lithium carbonate. Furthermore, the prepared battery-grade lithium carbonate contains the following contents: Na < 0.025%, Mg < 0.008%, Ca < 0.005%, K < 0.001%, Fe < 0.001%, Zn < 0.0003%, Cu < 0.0003%, Pb < 0.0003%, Si < 0.003%, Al < 0.001%, Mn < 0.0003%, Ni < 0.001%, and SO42-. 2- The content is <0.08, Cl - The content is <0.003, which meets the standard of "YS / T582-2013 Battery Grade Lithium Carbonate";

[0070] 6) Mother liquor recovery: The mother liquor obtained by combining the filtrate from step 4) and the filtrate from step 5) is frozen at 0°C for 4 hours to allow sodium sulfate decahydrate and sodium carbonate decahydrate to precipitate out. The mother liquor is then evaporated until white lithium carbonate precipitates out. After cooling to 60°C, it is filtered. The filtered material is returned to step 5) for washing, and the filtrate is returned to step 1) for recycling.

[0071] Example 4

[0072] A method for producing battery-grade lithium carbonate with purification and solvent inhibition includes the following steps:

[0073] 1) Primary purification: Cool 15000L of crude lithium sulfate solution with a lithium concentration of 30g / L to 4℃ and perform cold precipitation for 5h to precipitate sodium sulfate decahydrate (Na2SO4·10H2O). Then remove it by centrifugation and collect the centrifuged liquid to obtain the primary purified liquid.

[0074] 2) Secondary purification: the primary purified solution is warmed to 40°C, the pH of the solution is adjusted using a 40% sodium hydroxide solution, and the impurities are precipitated in stages. When the pH of the solution is adjusted to 7.5-8, the addition of sodium hydroxide is stopped, and iron and cobalt are converted into Fe(OH)3 and Co(OH)2, respectively. After 15 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 10-11, and the addition of sodium hydroxide is stopped to convert nickel and copper into (Ni(OH)2 and Cu(OH)2, respectively. After 15 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 12-14, and calcium and magnesium are converted into (Ca(OH)2 and Mg(OH)2, respectively. After 20 minutes of precipitation, 1000 mL of the secondary purified solution is added to 1000 mL of a 40% sodium hydroxide solution, and the mixture is stirred for 30 minutes. After the mixture is filtered, the filtrate is collected to obtain a tertiary purified solution. 3 After 20 minutes of standing, the solid is removed by filtration, and the filtrate is collected to obtain a secondary purified solution.

[0075] 3) Tertiary purification: the secondary purified solution is warmed to 40°C, the pH of the solution is adjusted to 6.5-7 using dilute sulfuric acid, and the solution is stirred. Then, 2.5 g / L of disodium ethylenediaminetetraacetate is added, followed by 2.5 g / L of oxalic acid after 15 minutes. After 30 minutes, 15 g / L of activated carbon is added to remove organic pigments. After 30 minutes, the solution is filtered, and the filtrate is warmed to 95°C and kept at this temperature for 30 minutes. The supernatant is clear and transparent, and the filtrate is collected to obtain a tertiary purified solution.

[0076] 4) Carbon synthesis: the content of Li (also referred to as the concentration of Li, in g / L) in the tertiary purified solution is determined. The content of Li is 31 g / L, and 40% Na2CO3 is slowly added to the tertiary purified solution at a rate of 22.7 g / L. When the pure alkali is added, the temperature of the solution should be controlled at 90°C, and the pH of the solution should be monitored at all times. When the pH is 12, the addition of pure alkali is stopped. When the pH drops to 8, it indicates that the carbonization is not complete, and the addition of pure alkali should be adjusted. When the pH is 9, the addition of pure alkali should be stopped. After 30 minutes of reaction, 3 g / L of dodecyl primary amine (dodecyl primary amine is dissolved and diluted in anhydrous ethanol at 30°C to prepare a solution with a concentration of 0.5 g / 100 mL) is added, and the reaction is carried out at 90°C for 30 minutes. The filter cake obtained is crude lithium carbonate.

[0077] 5) washing: first, add water to the crude lithium carbonate at a solid-liquid ratio of 1:4 and a temperature of 40°C for primary washing, as the solubility of Na2SO4 and Na2CO3 is the largest at 40°C, filter after washing for 35 min; then add water to the crude lithium carbonate obtained after primary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 60°C for secondary washing, filter after washing for 35 min; then add ethanol with a concentration of 40% to the crude lithium carbonate obtained after secondary washing and filtration at a solid-liquid ratio of 1:4 and a temperature of 80°C for tertiary washing, filter after washing for 35 min, and detect the contents of sulfate and calcium in the filtered material; after detection, if the contents of sulfate and calcium do not meet the standards, add water at a solid-liquid ratio of 1:1 and pass in CO2 gas for dissolution, and then heat to 90°C until complete dissolution, keep the temperature at 90°C for 40 min, and when the pH increases to 9, lithium carbonate reprecipitates, filter after keeping the temperature at 90°C for 40 min, dry the filtered material at 75°C for 5 h, and detect the content of lithium carbonate in the dried product; after detection, if the content of lithium carbonate is 99.95%≥99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained; and the contents of Na, Mg, Ca, K, Fe, Zn, Cu, Pb, Si, Al, Mn, Ni, SO4, and Cl in the prepared battery-grade lithium carbonate are <0.025%, <0.008%, <0.005, <0.001, <0.001, <0.0003, <0.0003, <0.0003, <0.003, <0.001, <0.0003, <0.001, <0.08, and <0.003, respectively, meeting the standards of YS / T 582-2013 Battery-Grade Lithium Carbonate; 2- -

[0078] 6) mother liquor recovery: freeze the mother liquor obtained by combining the filtrate after filtration in step 4) and the filtrate after filtration in step 5) at a temperature of 3°C for 4 h, so that sodium sulfate decahydrate and sodium carbonate decahydrate are precipitated, evaporate the mother liquor until white lithium carbonate is precipitated, filter after cooling to 60°C, and return the filtered material to step 5) for washing, and return the filtrate to step 1) for recycling.

[0079] Example 5

[0080] A purification and dissolution-resistant production method of battery-grade lithium carbonate, comprising the following steps:

[0081] 1) primary purification: cool 15000 L of crude lithium sulfate solution with a lithium concentration of 40 g / L to 4°C, and centrifuge after precipitation for 5 h to remove sodium sulfate decahydrate (Na2SO4·10H2O), collect the centrifugal liquid, and obtain a primary purification liquid;

[0082] ​​2) Secondary purification: the primary purified solution is warmed to 40°C, the pH of the solution is adjusted using a 40% sodium hydroxide solution, and the impurities are precipitated in stages. When the pH of the solution is adjusted to 7.5-8, the addition of sodium hydroxide is stopped, and iron and cobalt are converted into Fe(OH)3 and Co(OH)2, respectively. After 15 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 10-11, and the addition of sodium hydroxide is stopped to convert nickel and copper into (Ni(OH)2 and Cu(OH)2, respectively. After 15 minutes of precipitation, the addition of sodium hydroxide is continued to adjust the pH of the solution to 12-14, and calcium and magnesium are converted into (Ca(OH)2 and Mg(OH)2, respectively. After 20 minutes of precipitation, 1000 mL of the secondary purified solution is mixed with 0.5 g of polyacrylamide, and the mixture is allowed to stand for 20 minutes. The solid is removed by filtration, and the filtrate is collected to obtain a tertiary purified solution. 3 After the addition of polyacrylamide (0.5 g of polyacrylamide is dissolved in 300 mL of water to prepare a solution), the mixture is allowed to stand for 20 minutes. The solid is removed by filtration, and the filtrate is collected to obtain a secondary purified solution.

[0083] 3) Tertiary purification: the secondary purified solution is warmed to 40°C, the pH of the solution is adjusted to 6.5-7 using dilute sulfuric acid, and the solution is stirred. Then, 2.5 g / L of disodium ethylenediaminetetraacetate is added, followed by the addition of 2.5 g / L of oxalic acid after 15 minutes. After 30 minutes, 15 g / L of activated carbon is added to remove organic pigments. After 30 minutes, the solution is filtered. Then, the filtrate is warmed to 95°C and maintained at this temperature for 30 minutes. The supernatant is observed, and the filtrate is collected to obtain a tertiary purified solution.

[0084] 4) Carbon synthesis: the content of Li (also referred to as the concentration of Li, in g / L) in the tertiary purified solution is determined. The content of Li is measured to be 41 g / L. Solid Na2CO3 is slowly added to the tertiary purified solution at a dosage of 30 g / L. When adding the solid Na2CO3, the temperature of the solution should be controlled at 90°C, and the pH of the solution should be monitored in real time. When the pH is 12, the addition of solid Na2CO3 is stopped. When the pH drops to 8, it indicates that the carbonization is not complete, and the addition of solid Na2CO3 should be adjusted slowly to adjust the pH. When the pH is 9, the addition of solid Na2CO3 should be stopped. After 30 minutes of reaction, 3 g / L of dodecylamine (dodecylamine is dissolved and diluted in anhydrous ethanol at 30°C to prepare a solution with a concentration of 0.5 g / 100 mL) is added. The reaction is carried out at 90°C for 30 minutes, and the filter cake obtained is a crude lithium carbonate.

[0085] 5) washing: first, add water to the crude lithium carbonate at a solid-liquid ratio of 1:4 at a temperature of 40°C for a first washing, at which the solubility of Na2SO4 and Na2CO3 is the largest at 40°C, filter after washing for 35 min; then add water to the crude lithium carbonate obtained after the first washing and filtration at a solid-liquid ratio of 1:4 at a temperature of 60°C for a second washing, filter after washing for 35 min; then add ethanol with a concentration of 40% to the crude lithium carbonate obtained after the second washing and filtration at a solid-liquid ratio of 1:4 at a temperature of 80°C for a third washing, filter after washing for 35 min, and detect the contents of sulfate and calcium in the filtered material; after detection, if the contents of sulfate and calcium do not meet the standards, add water at a solid-liquid ratio of 1:1 and pass in CO2 gas for dissolution, and then heat to 90°C after complete dissolution, keep the temperature at 90°C for 40 min, when the pH rises to 9, lithium carbonate reprecipitates, filter after keeping the temperature at 90°C for 40 min, and dry the filtered material at 75°C for 5 h, and detect the content of lithium carbonate in the dried product; after detection, if the content of lithium carbonate in the dried product is <99.5%, the product still needs to be treated by calcination and dissolution, and the specific operation steps of the calcination and dissolution treatment are as follows: add water to the dried product at a solid-liquid ratio of 1:3 at a temperature of 90°C for washing for 50 min, filter, dry the filtered material at 75°C for 5 h, and detect the content of lithium carbonate in the dried product; after detection, if the content of lithium carbonate is 99.95%≥99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained; and the contents of Na, Mg, Ca, K, Fe, Zn, Cu, Pb, Si, Al, Mn, Ni, SO4, and Cl in the prepared battery-grade lithium carbonate are <0.025%, <0.008%, <0.005, <0.001, <0.001, <0.0003, <0.0003, <0.0003, <0.003, <0.001, <0.0003, <0.001, <0.08, and <0.003, respectively, meeting the standards of YS / T 582-2013 Battery-Grade Lithium Carbonate. 2- -

[0086] 6) mother liquor recovery: freeze the mother liquor obtained by combining the filtrate after filtration in step 4) and the filtrate after filtration in step 5) at a temperature of 3°C for 4 h, so that sodium sulfate decahydrate and sodium carbonate decahydrate are precipitated, evaporate the mother liquor until white lithium carbonate is precipitated, cool to 60°C, and filter, and return the filtered material to step 5) for washing, and return the filtrate to step 1) for recycling.

[0087] Comparative Example 1

[0088] ​​The difference between this comparative example and Example 1 is that activated carbon is not added in step 3) of the tertiary purification. The specific operation of this step is as follows: the secondary purified solution is heated to 40°C, the pH of the solution is adjusted to 6.5-7 using dilute sulfuric acid, stirred well, and then 2.5 g / L of disodium ethylenediaminetetraacetate is added first for 15 minutes, followed by 2.5 g / L of oxalic acid. After 30 minutes, the solution is filtered, and the filtrate is then heated to 95°C and kept at that temperature for 30 minutes. The supernatant solution is observed after standing; if it is clear and transparent, it is filtered and the filtrate is collected to obtain the tertiary purified solution. The other steps are the same as in Example 1.

[0089] Comparative Example 2

[0090] This comparative example uses the three-stage purification solution prepared in Example 1 for steps 4)-6). The difference between steps 4)-6) and those in Example 1 is that in step 4), a 40% Na2CO3 solution is added during carbonization synthesis. Specifically, the 40% Na2CO3 solution is slowly added to the three-stage purification solution at a dosage of 5.1 g / L. The solution temperature should be controlled at 90°C during the addition of soda ash, and the solution should be added in multiple batches while continuously monitoring the pH. When the pH reaches 12, the addition of soda ash is stopped. When the pH drops to 8, it indicates incomplete carbonization, and soda ash should be added slowly to adjust the pH. When the pH reaches 9, the addition of soda ash is stopped, indicating sufficient alkali has been added. After maintaining the temperature for 30 minutes, dodecylamine (prepared by dissolving and diluting dodecylamine in anhydrous ethanol at 30°C, with a concentration of 0.5 g / 100 mL) is added at a dosage of 3 g / L. The reaction is carried out at 90°C for 30 minutes, followed by filtration. The resulting filter cake is crude lithium carbonate. The other steps are the same as in Example 1.

[0091] Comparative Example 3

[0092] This comparative example uses the tertiary purification solution prepared in Example 2 for steps 4)-6). The difference between steps 4)-6) and those in Example 2 is that solid Na2CO3 is added during carbonization synthesis in step 4). Specifically, solid Na2CO3 is slowly added to the tertiary purification solution at a dosage of 9.5 g / L. The solution temperature should be controlled at 90°C during the addition of soda ash, and the addition should be done in multiple batches, while continuously monitoring the pH change. When the pH reaches 12, the addition of soda ash is stopped. When the pH drops to 8, it indicates incomplete carbonization, and soda ash should be added slowly to adjust the pH. When the pH reaches 9, the addition of soda ash is stopped, indicating sufficient alkali has been added. After reacting at this temperature for 30 minutes, dodecylamine (prepared by dissolving and diluting in anhydrous ethanol at 30°C, with a concentration of 0.5 g / 100 mL) is added at a dosage of 2 g / L. The reaction is carried out at 90°C for 30 minutes, followed by filtration. The resulting filter cake is crude lithium carbonate. Other steps are the same as in Example 2.

[0093] Comparative Example 4

[0094] Comparative Example 4 was prepared by using the tertiary purification solution prepared in Example 3 to perform the operation steps of 4) to 6), wherein the difference between the operation steps of 4) to 6) of Comparative Example 4 and Example 1 was that solid Na2CO3 was added in the carbonation synthesis of step 4). The specific operation of this step was as follows: solid Na2CO3 was slowly added into the tertiary purification solution at a dosage of 15.4 g / L, and the temperature of the solution should be controlled at 90°C when adding the solid Na2CO3, and the solution pH should be detected at any time during the addition; when the pH was 12, the addition of the solid Na2CO3 was stopped; when the pH dropped to 8, it indicated that the carbonation was not complete, and the addition of the solid Na2CO3 should be slowly adjusted to adjust the pH; when the pH was 9, the addition of the solid Na2CO3 was stopped, and 2.5 g / L of dodecyl primary amine (dodecyl primary amine was dissolved and diluted in anhydrous ethanol at 30°C to prepare a solution with a concentration of 0.5 g / 100 mL) was added after the solution was kept at 90°C for 30 min, and the solution was reacted at 90°C for 30 min, and then filtered to obtain a filter cake of crude lithium carbonate. The other steps were the same as those of Example 3.

[0095] Comparative Example 5

[0096] Comparative Example 5 was prepared by using the tertiary purification solution prepared in Example 1 to perform the operation steps of 4) to 6), wherein the difference between the operation steps of 4) to 6) of Comparative Example 5 and Example 1 was that no dodecyl primary amine was added in the carbonation synthesis of step 4). The specific operation of this step was as follows: solid Na2CO3 was slowly added into the tertiary purification solution at a dosage of 5.1 g / L, and the temperature of the solution should be controlled at 90°C when adding the solid Na2CO3, and the solution pH should be detected at any time during the addition; when the pH was 12, the addition of the solid Na2CO3 was stopped; when the pH dropped to 8, it indicated that the carbonation was not complete, and the addition of the solid Na2CO3 should be slowly adjusted to adjust the pH; when the pH was 9, the addition of the solid Na2CO3 was stopped, and the solution was filtered after being kept at 90°C for 30 min to obtain a filter cake of crude lithium carbonate. The other steps were the same as those of Example 3.

[0097] Comparative Example 6

[0098] The comparative example 1 uses the crude lithium carbonate prepared in the example 1 to perform the operation steps of 5) and 6), which are different from the example 1 in that the step 5) is washed with water three times. The specific operation of this step is as follows: first, the crude lithium carbonate is added with water at a temperature of 40 DEG C according to a solid-liquid ratio of 1:4 to perform a first washing, and the Na2SO4 and Na2CO3 have the maximum solubility at 40 DEG C, and after washing for 35 min, the mixture is filtered; then, the crude lithium carbonate obtained after the first washing and filtering is added with water at a temperature of 60 DEG C according to a solid-liquid ratio of 1:4 to perform a second washing, and after washing for 35 min, the mixture is filtered; then, the crude lithium carbonate obtained after the second washing and filtering is added with water at a temperature of 80 DEG C according to a solid-liquid ratio of 1:4 to perform a third washing, and after washing for 35 min, the mixture is filtered, and the filtered material is directly dried at 75 DEG C for 5 h to obtain a dried product, which is a battery-grade lithium carbonate.

[0099] Comparative example 7

[0100] The comparative example 1 uses the crude lithium carbonate prepared in the example 1 to perform the operation steps of 5) and 6), which are different from the example 1 in that the step 5) is washed with water three times. The specific operation of this step is as follows: first, the crude lithium carbonate is added with water at a temperature of 40 DEG C according to a solid-liquid ratio of 1:4 to perform a first washing, and the Na2SO4 and Na2CO3 have the maximum solubility at 40 DEG C, and after washing for 35 min, the mixture is filtered; then, the crude lithium carbonate obtained after the first washing and filtering is added with water at a temperature of 60 DEG C according to a solid-liquid ratio of 1:4 to perform a second washing, and after washing for 35 min, the mixture is filtered; then, the crude lithium carbonate obtained after the second washing and filtering is added with water at a temperature of 80 DEG C according to a solid-liquid ratio of 1:4 to perform a third washing, and after washing for 35 min, the mixture is filtered, and the filtered material is directly dried at 75 DEG C for 5 h to obtain a dried product, which is a battery-grade lithium carbonate.

[0101] Comparative example 8

[0102] The comparative example 1 uses the crude lithium carbonate prepared in the example 1 to perform the operation steps of 5) and 6), which are different from the example 1 in that the step 5) is washed with water three times. The specific operation of this step is as follows: first, the crude lithium carbonate is added with water at a temperature of 40 DEG C according to a solid-liquid ratio of 1:4 to perform a first washing, and the Na2SO4 and Na2CO3 have the maximum solubility at 40 DEG C, and after washing for 35 min, the mixture is filtered; then, the crude lithium carbonate obtained after the first washing and filtering is added with water at a temperature of 60 DEG C according to a solid-liquid ratio of 1:4 to perform a second washing, and after washing for 35 min, the mixture is filtered; then, the crude lithium carbonate obtained after the second washing and filtering is added with water at a temperature of 80 DEG C according to a solid-liquid ratio of 1:4 to perform a third washing, and after washing for 35 min, the mixture is filtered, and the filtered material is directly dried at 75 DEG C for 5 h to obtain a dried product, which is a battery-grade lithium carbonate.

[0103] The operation methods for preparing the battery-grade lithium carbonate in the examples 1-5 and the comparative examples 1-8 are different, as shown in Table 1:

[0104] Table 1: Difference table of operation methods for producing battery-grade lithium carbonate in the examples 1-5 and the comparative examples 1-8

[0105]

[0106]

[0107] Note: In the above table, indicates that the corresponding operation step is performed; indicates that the corresponding operation step is not performed.

[0108] The yield, purity and whiteness of the battery-grade lithium carbonate produced in the examples 1-5 and the comparative examples 1-8 are determined, wherein the calculation formula of the yield is the mass of lithium in the battery-grade lithium carbonate / the mass of lithium in the crude lithium sulfate solution x 100%, the purity of lithium carbonate is determined according to the method in YS / T 582-2013 Battery-Grade Lithium Carbonate, and the whiteness is determined according to the method in Q / 320684 FUT01-2017 Battery-Grade Lithium Carbonate, and the detection results are shown in Table 2:

[0109] Table 2: Yield, purity and whiteness of the battery-grade lithium carbonate produced in the examples 1-5 and the comparative examples 1-8

[0110] Yield / % Purity / % Brightness / % Example 1 99.6 99.98 97 Example 2 99.4 99.97 97 Example 3 99.3 99.96 97 Example 4 99.1 99.95 96 Example 5 99.2 99.95 96 Comparative Example 1 99 98 85 Comparative Example 2 80 99.92 90 Comparative Example 3 90 99.91 90 Comparative Example 4 77 99.9 90 Comparative Example 5 82 99 80 Comparative Example 6 86 96 88 Comparative Example 7 95.2 99.68 75 Comparative Example 8 90 99.91 70

[0111] From the analysis of Table 1 and Table 2, compared with Example 1, the addition of activated carbon for adsorption in the third purification step for producing battery-grade lithium carbonate in Comparative Example 1, the whiteness of the battery-grade lithium carbonate produced in Comparative Example 1 is only 85%, which is decreased by 12.4% based on Example 1, indicating that the addition of activated carbon can effectively adsorb organic pigments in the solution, so that the organic pigments in the solution can be effectively removed, thereby greatly improving the whiteness of the produced lithium carbonate;

[0112] Compared with Example 1, the addition of Na2CO3 solution to the third purification solution with a Li content of 7 g / L in the carbonization synthesis step for producing battery-grade lithium carbonate in Comparative Example 2, the yield of the battery-grade lithium carbonate produced in Comparative Example 2 is only 80%, which is decreased by 19.7% based on Example 1, because: adding liquid Na2CO3 solution to the third purification solution with a Li content of less than 8 g / L, due to the too low concentration of the solution, the addition of Na2CO3 solution will increase the water content in the solution, further reducing the Li content in the third purification solution, resulting in a significant reduction in the collision opportunity between ions, thereby reducing the conversion rate of Li2CO3 and the yield of Li2CO3;

[0113] Compared with Example 2, the addition of solid Na2CO3 to the third purification solution with a Li content of 13 g / L in the carbonization synthesis step for producing battery-grade lithium carbonate in Comparative Example 3, the yield of the battery-grade lithium carbonate produced in Comparative Example 3 is 90%, which is slightly decreased by 0.1% based on Example 2, because: adding solid Na2CO3 to the third purification solution with a Li content of 8-15 g / L, the concentration of the solution is slightly high, if solid Na2CO3 is added, a small part of Na2CO3 will be difficult to dissolve, reducing the conversion effect of Li2CO3, thereby reducing the yield of Li2CO3;

[0114] Compared with Example 3, the addition of solid Na2CO3 to the third purification solution with a Li content of 21 g / L in the carbonization synthesis step for producing battery-grade lithium carbonate in Comparative Example 4, the yield of the battery-grade lithium carbonate produced in Comparative Example 3 is only 77%, which is decreased by 22.5% based on Example 3, because: adding solid Na2CO3 to the third purification solution with a Li content of more than 15 g / L, the concentration of the solution is very high, if solid Na2CO3 is added, most of Na2CO3 will be difficult to dissolve, forming a package, reducing the conversion effect of Li2CO3, thereby significantly reducing the yield of Li2CO3;

[0115] Compared with Example 1, the addition of dodecyl primary amine in the carbonization synthesis step of producing battery-grade lithium carbonate is not added in Comparative Example 5, and the yield of battery-grade lithium carbonate produced by Comparative Example 5 is only 82%, and the whiteness is only 80%, which is 17.7% and 17.5% lower than the yield and whiteness of Example 1 respectively, indicating that the addition of dodecyl primary amine can not only effectively prevent the dissolution of Li2CO3 in the solution, but also greatly improve the yield of Li2CO3, and significantly improve the whiteness of Li2CO3.

[0116] Compared with Example 1, the use of ethanol as the washing liquid in the washing step of producing battery-grade lithium carbonate in Comparative Example 6 is used in the third washing, and the yield of battery-grade lithium carbonate produced by Comparative Example 6 is only 86%, and the whiteness is only 88%, which is 13.7% and 9.3% lower than the yield and whiteness of Example 1 respectively, indicating that the use of ethanol as the washing liquid in the third washing can not only effectively prevent the dissolution of Li2CO3, reduce the loss of Li2CO3 in the washing process, and improve the yield of Li2CO3, but also improve the whiteness of Li2CO3 to a certain extent.

[0117] In addition, the yield of battery-grade lithium carbonate produced by the purification and dissolution prevention method of the present application (Examples 1-5) is higher than 99%, the purity is higher than 99.95%, and the whiteness is higher than 95%, the yield and purity of the battery-grade lithium carbonate prepared thereby are higher than those of the battery-grade lithium carbonate prepared by Comparative Example 7 and Comparative Example 8, and the whiteness of the battery-grade lithium carbonate prepared thereby meets the standard of superior product, and the whiteness is significantly greater than that of Comparative Example 7 and Comparative Example 8, indicating that the purification and dissolution prevention method of the present application can not only improve the yield and purity of battery-grade lithium carbonate, but also significantly increase the whiteness of battery-grade lithium carbonate, and realize safe and environmentally friendly production with high purity, high yield and high whiteness.

[0118] Experimental example of the effect of the addition of dodecyl primary amine on the whiteness and yield of the produced battery-grade lithium carbonate

[0119] This experimental example refers to the method of Example 1 to study the effect of the addition of dodecyl primary amine on the whiteness and yield of the produced battery-grade lithium carbonate, and the dodecyl primary amine with an amount of 0 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L and 5 g / L is added in the carbonization synthesis step, and each amount group is prepared with battery-grade lithium carbonate in three parallel experiments, and the yield and whiteness of the prepared battery-grade lithium carbonate are determined, and then SPSS is used for single factor variance analysis of the data to investigate whether different amounts of dodecyl primary amine have a significant effect on the yield and whiteness of the produced battery-grade lithium carbonate, and the data analysis results are shown in Tables 3-6:

[0120] From Table 4, in the variance homogeneity test results, the whiteness shows a significance of 1.000>0.05, and the yield shows a significance of 0.164>0.05, both of which are greater than 0.05, indicating that the variance is homogeneous, and the applicable conditions of variance analysis are met.

[0121] From Table 5, the single-factor variance analysis results, the whiteness and yield show a significance of 0.000<0.05, indicating that the whiteness and yield have significant differences, and therefore the amount of dodecyl primary amine has a significant effect on the whiteness and yield of the battery-grade lithium carbonate.

[0122] Table 3 describes

[0123]

[0124] Table 4 Variance homogeneity test

[0125]

[0126] Table 5 ANOVA

[0127]

[0128] Table 6 Multiple comparison LSD

[0129]

[0130]

[0131]

[0132] *. The significance level of the mean difference is 0.05.

[0133] From Table 3 and 6, when the amount of dodecyl primary amine is 0 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, and 5 g / L, the average values of whiteness and yield and the significant difference table are shown in Table 7:

[0134] Table 7 Average values of whiteness and yield and significant difference table

[0135]

[0136] In this experiment, the amount of dodecyl primary amine and the data of whiteness and yield were fitted by equation, and the results are shown in Figure 2 and Figure 3 .

[0137] From Figure 2 , the equation between the amount of dodecyl primary amine and whiteness is y=1.964x 2 +11.564x+79.929, R 2=0.9918, indicating a good correlation between the amount of dodecylamine used and the whiteness of the produced battery-grade lithium carbonate; and as shown in Table 7, with the increase of the amount of dodecylamine used, the whiteness first increases significantly and then decreases significantly. There is no significant difference in whiteness between the amounts of 2 g / L and 3 g / L.

[0138] Depend on Figure 3 It can be seen that the equation relating the amount of dodecyl primary amine used to the yield is y = 1.9625x 2 +11.958x+82.111, R 2 =0.9945, indicating a good correlation between the amount of dodecylamine used and the yield of battery-grade lithium carbonate produced; and as shown in Table 7, the yield first increases significantly and then decreases significantly with the increase of the amount of dodecylamine used. There is no significant difference in yield among the dosages of 2 g / L, 3 g / L and 4 g / L.

[0139] Based on the above analysis, it can be seen that the addition and dosage of dodecylamine will affect the whiteness and yield of the produced battery-grade lithium carbonate. Considering the cost of using dodecylamine, the dosage of dodecylamine is selected to be 2-3 g / L.

[0140] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for producing battery-grade lithium carbonate with purification and solvent inhibition, characterized in that, Includes the following steps: 1) Primary purification: The crude lithium sulfate solution is cooled and precipitated to allow sodium sulfate decahydrate to precipitate. The sodium sulfate is then removed by solid-liquid separation to obtain the primary purified solution. 2) Secondary purification: The primary purified liquid is heated to 40℃, the pH of the solution is adjusted with sodium hydroxide, impurities are precipitated in stages, flocculant is added and the solution is allowed to stand, filtered and the filtrate is collected to obtain the secondary purified liquid. 3) Tertiary purification: Heat the secondary purification solution to 40℃, adjust the pH of the solution to 6.5-7 using sulfuric acid, first add disodium ethylenediaminetetraacetate and oxalic acid, then add activated carbon to adsorb and remove organic pigments, filter, then heat the filtrate to 90-95℃, keep it at this temperature for 30 minutes, observe the supernatant solution of the precipitate after standing, if it is clear and transparent, filter and collect the filtrate to obtain the tertiary purification solution; 4) Carbonization synthesis: The Li content in the tertiary purification solution was determined, and solid Na2CO3 or Na2CO3 solution was slowly added to the tertiary purification solution at 90℃ according to the Li content × 1.465 × 0.5 as the amount of alkali to be added until the pH of the solution reached 9. The reaction was maintained at this temperature for 30 min. Then, dodecylamine was added, and the reaction was carried out at 90℃ for 30 min. After filtration, the filter cake obtained was crude lithium carbonate. 5) Washing: First, wash the crude lithium carbonate twice with water and filter it. Then, wash it a third time with ethanol. After filtration, dry it to obtain battery-grade lithium carbonate. 6) Mother liquor recovery: The mother liquor obtained by combining the filtrate filtered in step 4) and the filtrate filtered in step 5) is recycled.

2. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, In step 1), the temperature during cooling and refrigeration is 3-5℃, and the refrigeration time is 4-6h.

3. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, The specific steps for the staged precipitation of impurities in step 2) are as follows: When the pH of the solution is adjusted to 7.5-8, stop adding sodium hydroxide to convert iron and cobalt into Fe(OH)3 and Co(OH)2, respectively. After precipitation for 10-20 minutes, continue adding sodium hydroxide to adjust the pH of the solution to 10-11, stop adding sodium hydroxide, and convert nickel and copper into Ni(OH)2 and Cu(OH)2, respectively. After precipitation for 10-20 minutes, continue adding sodium hydroxide to adjust the pH of the solution to 12-14 to convert calcium and magnesium into Ca(OH)2 and Mg(OH)2, respectively. After precipitation for 10-30 minutes.

4. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, In step 3), the dosage of disodium ethylenediaminetetraacetate and oxalic acid is 2-3 g / L, and the dosage of activated carbon is 10-20 g / L.

5. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, The standard for adding solid Na2CO3 or Na2CO3 solution to the tertiary purification solution in step 4) is as follows: when the Li content is less than 8 g / L, add solid Na2CO3; when the Li content is greater than 15 g / L, add Na2CO3 solution with a concentration of 30-40%.

6. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, The amount of dodecyl primary amine used is 2-3 g / L.

7. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, The specific washing steps in step 5) are as follows: First, add water at 40°C to the crude lithium carbonate at a solid-liquid ratio of 1:4 for a first wash, washing for 30-40 minutes, then filter. Next, add water to the crude lithium carbonate obtained after the first wash and filtration at a solid-liquid ratio of 1:4 and wash a second time at 55-60°C for 30-40 minutes, then filter. Then, add 40% ethanol to the crude lithium carbonate obtained after the second wash and filtration at a solid-liquid ratio of 1:4 and wash a third time at 60-90°C for 30-40 minutes, then filter. Detect the sulfate and calcium content in the filtered material. If the sulfate and calcium content meets the standards, directly dry the filtered material at 70-80°C for 4-6 hours, and determine the lithium carbonate content in the dried product. If the lithium carbonate content is ≥99.5%, the dried product is qualified, and battery-grade lithium carbonate is obtained.

8. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 7, characterized in that, If the sulfate and calcium content in the filtered material does not meet the standards, add water at a solid-liquid ratio of 1:1 and pass CO2 gas to dissolve it. After complete dissolution, raise the temperature to 90℃ and keep it at that temperature for 30-40 minutes. When the pH rises to 9, lithium carbonate will re-precipitate. Keep it at 90℃ for 30-40 minutes and then filter it. Dry the filtered material at 70-80℃ for 4-6 hours. If the lithium carbonate content is greater than 99.5%, the dried product is qualified and battery-grade lithium carbonate is obtained.

9. A method for producing purified and solvent-inhibited battery-grade lithium carbonate as described in claim 7 or 8, characterized in that, If the lithium carbonate content in the measured dried product is <99.5%, then a coking process is required. The specific steps of the coking process are as follows: add water to the dried product at a solid-liquid ratio of 1:3, wash at 90°C for 30-50 minutes, filter, and dry the filtered material at 70-80°C for 4-5 hours to obtain battery-grade lithium carbonate.

10. The purification and solvent-inhibiting production method for battery-grade lithium carbonate as described in claim 1, characterized in that, The specific operation steps of step 6) are as follows: the mother liquor obtained by combining the filtrate filtered in step 4) and the filtrate filtered in step 5) is frozen at a temperature of 0-5℃ for 4 hours to allow sodium sulfate decahydrate and sodium carbonate decahydrate to precipitate out. The mother liquor is then evaporated until white lithium carbonate precipitates out. After cooling to 60℃, it is filtered, and the filtered material is returned to step 5) for washing. The filtrate is returned to step 1) for recycling.

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