Method for preparing high-purity lithium carbonate based on microbubble-assisted method

Abstract

The invention discloses a method for preparing high-purity lithium carbonate based on a micro-bubble auxiliary method, and aims to solve the problems of high CO2 consumption, low mass transfer rate, low conversion rate, low lithium yield, low purity and the like in the process of preparing the high-purity lithium carbonate by a traditional carbonization method, and a micro-nano bubble generator is used for carrying out auxiliary carbonization reaction on crude lithium carbonate. The introduction of the micro-nano generator enables CO2 gas to be dissolved in water more quickly, and the micro-nano bubble generator can enhance gas-liquid mass transfer and CO2 absorption, improve local supersaturation and inhibit crystal growth, so that the dissolution of lithium carbonate in water is accelerated, and lithium bicarbonate with higher solubility is generated. In addition, the ion exchange resin has a high removal effect on low-concentration impurity ions in the LiHCO3 solution, and the purity of the high-purity lithium carbonate can reach 99.99% or above. Mother liquor and carbon dioxide can be recycled in the process, and no by-product is generated. The method is more thorough in dissolution in the carbonization process, higher in product purity, more environment-friendly and simpler, and the whole technological process is simple and feasible.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium carbonate purification, and particularly relates to a method for preparing high-purity lithium carbonate based on a microbubble-assisted method. Background Art

[0002] The core component of new energy vehicles lies in the power battery, which is composed of a positive electrode, a negative electrode, a separator, an electrolyte, and a housing. The main raw materials of the electrolyte are high-purity lithium carbonate, lithium hexafluorophosphate, etc. Therefore, the development of the new energy vehicle industry and the market demand for energy storage batteries have brought once-in-a-lifetime opportunities and challenges to lithium-based battery materials such as high-purity lithium carbonate (Li 2 CO 3 ).

[0003] Currently, most Li 2 CO 3 is produced from salt lake brine, and the process of directly extracting Li 2 CO 3 only meets the industrial grade (crude product) or battery grade standards and does not meet the application requirements of power batteries. Therefore, the crude product Li 2 CO 3 needs to be additionally processed using a new purification technology to meet its standards. The main methods include the causticization method, the electrolysis method, and the carbonization method. The reaction process of the causticization method is complex, expensive, and introduces high-concentration impurity ions. The electrolysis method is not conducive to industrial production due to high energy consumption. Therefore, the carbonization method is the optimal choice. In the carbonization step, the crude product Li 2 CO 3 is mixed with ultrapure water to form a Li 2 CO 3 slurry. Then it is evaporated and decomposed into high-purity lithium carbonate. However, the carbonization method still has some problems, such as low mass transfer rate, low lithium concentration, low yield, high carbon dioxide consumption, and long carbonization time (150 min), etc. Considering the problems existing in the traditional carbonization method, it is of great significance to develop a more effective method for preparing high-purity lithium carbonate.

[0004] Micro-nano bubbles are extremely fine bubbles with a diameter less than 50 microns. Micro-nano bubbles have a slow rising speed, a long residence time, a high dissolution efficiency in water, and possess characteristics such as self-aeration, negatively charged, and rich in strongly oxidizing free radicals. For ordinary bubbles, the solubility of gas is often affected by the environment and saturation. However, micro-nano bubbles gradually shrink into the nanoscale during the slow rising process, disappear and dissolve in water, thereby greatly improving the solubility of gas in water. This makes micro-nano bubbles have broad application prospects in water treatment. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention uses a microbubble generator to assist the pressure carbonation reaction of crude lithium carbonate and optimize various carbonation parameters, aiming to provide a method for preparing high-purity lithium carbonate based on the microbubble-assisted method.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing high-purity lithium carbonate based on the microbubble-assisted method, specifically including the following steps:

[0008] Step 1, weigh a certain amount of crude lithium carbonate prepared from salt lake brine and add it to a container for standby;

[0009] Step 2, add ultrapure water to the above container according to a solid-liquid ratio of 1:20 to 40 to obtain a mixed liquid;

[0010] Step 3, insert the CO 2 gas and the aeration head of the micro-nano bubble generator into the mixed liquid;

[0011] Step 4, under the conditions of a temperature of 20 to 35 °C, a stirring speed of ≥200 rpm / min, a CO 2 flow rate of 0.25 to 1.5 L / min, a time of 40 to 150 min, and a micro-nano bubble generator flow rate of 2.5 L / min, carry out a carbonation reaction to generate a LiHCO 3 solution, and recycle the unreacted CO 2 ;

[0012] Step 5, remove impurities from the LiHCO 3 solution through ion exchange resin to obtain a LiHCO 3 solution after removing impurities;

[0013] Step 6, carry out a hydrothermal evaporation decomposition reaction on the LiHCO 3 solution after removing impurities, with a reaction temperature of ≥90 °C, a stirring speed of ≥400 rpm / min, and a reaction time of 60 to 150 min, and finally obtain a high-purity lithium carbonate solution;

[0014] Step 7, carry out hot filtration on the high-purity lithium carbonate solution, recycle the mother liquor, and dry the solid in a vacuum oven at 110 °C for 120 min to obtain a dry high-purity lithium carbonate solid;

[0015] Step 8, wash the dry high-purity lithium carbonate solid, dissolve it according to a solid-liquid ratio of 1:5 to 15 with ultrapure water, and wash it at a temperature of 75 to 85 °C for 30 min; then carry out hot filtration, recycle the mother liquor, and dry the solid in a vacuum oven at 110 °C for 120 min to obtain the final high-purity lithium carbonate, detect and analyze its impurity content, and compare it with the crude lithium carbonate.

[0016] Further, in the step 1, the container is a three-necked flask or a glass reactor, and the weighing amount of the crude lithium carbonate is 50-100 g.

[0017] Further, in the step 2, ultrapure water is added according to a solid-liquid ratio of 1:30-40, and the ultrapure water can be replaced by the recycled mother liquor in the step 7 or 8.

[0018] Further, in the step 3, the purity of the CO 2 gas is ≥99.9%.

[0019] Further, in the step 4, in the carbonization reaction, the temperature is 25 °C, the stirring speed is 250-400 rpm / min, the CO 2 flow rate is 1 L / min, the time is 120 min, and the flow rate of the micro-nano bubble generator is 2.5 L / min.

[0020] Further, in the step 5, the model of the ion exchange resin is LS1000; the addition amount of the ion exchange resin is 450-550 g.

[0021] Further, in the step 6, the temperature of the hydrothermal evaporation decomposition reaction is 90 °C, the stirring speed is 400 rpm / min, and the reaction time is 90 min.

[0022] Further, in the step 8, the pulping is dissolved by adding ultrapure water according to a solid-liquid ratio of 1:5-10, and the pulping is carried out at a temperature of 85 °C for 30 min; the purity of the final high-purity lithium carbonate is 99.997%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In view of the problems of high CO 2 consumption, low mass transfer rate, low conversion rate, low lithium yield, and low purity in the process of preparing high-purity lithium carbonate by the traditional carbonization method, in order to solve the above problems, a micro-nano bubble generator is used to assist the carbonization reaction of the crude lithium carbonate. The introduction of the micro-nano generator will make the CO 2 gas dissolve in water faster. The micro-nano bubble generator can enhance gas-liquid mass transfer and CO 2 absorption, improve local supersaturation, inhibit crystal growth, and thus accelerate the dissolution of lithium carbonate in water to form lithium bicarbonate with a greater solubility. In addition, the ion exchange resin has a significant influence on the removal of Na 3 , K + , Ca + and Mg 2+ in the LiHCO 2+ solution, and has a significant influence on LiHCO 3The removal effect of low-concentration impurity ions in the solution is relatively high, and the purity of high-purity lithium carbonate can reach over 99.99%. This method can reduce the particle size of the final product from 40 μm to within 15 μm, and increase the conversion rate to 20-30%. During the whole process, the mother liquor and carbon dioxide can be reused without by-products. In summary, the carbonization process of this method is more thorough, the product purity is higher, it is more environmentally friendly and simple, and the whole process flow is simple and feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the process flow chart of the method of the present invention;

[0026] Figure 2 for different CO 2 flow rate on the carbonization rate;

[0027] Figure 3 is the effect of different solid-liquid ratios on the carbonization rate;

[0028] Figure 4 is the effect of different reaction times on the carbonization rate;

[0029] Figure 5 is the effect of different carbonization reaction temperatures on the carbonization rate;

[0030] Figure 6 is the diagram of the effect of the stirring speed of the carbonization reaction on the carbonization rate;

[0031] Figure 7 is the effect of the resin dosage on the impurity removal rate;

[0032] Figure 8 is the effect of the hydrothermal evaporation decomposition reaction temperature on the lithium carbonate yield

[0033] Figure 9 is the effect of different hydrothermal evaporation decomposition stirring speeds on the lithium carbonate yield. DETAILED DESCRIPTION OF THE INVENTION

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] In the description of the present invention, the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0036] Example 1

[0037] Optimization method for carbonization reaction parameters

[0038] 1. Influence of different CO 2 flow rate on carbonization rate

[0039] Weigh 50 g of crude lithium carbonate prepared from salt lake brine and add it to a three-necked flask; add 1500 mL of ultrapure water to the three-necked flask according to a solid-liquid ratio of 1:30 to obtain a mixed liquid; insert the CO 2 gas and the aeration head of the micro-nano bubble generator into the mixed liquid; under the conditions of a temperature of 25 °C, a stirring speed of 350 rpm / min, a CO 2 flow rate of 0.25, 0.5, 1, 1.5 L / min, a time of 120 min, and a flow rate of the micro-nano bubble generator of 2.5 L / min, carry out a carbonization reaction to generate a LiHCO 3 solution, and calculate the carbonization rate of the LiHCO 3 solution; the carbonization rate where n represents the amount of substance of Li + in mol; M represents the molar mass of Li 2 CO 3 in g / mol; m represents the initial mass of Li 2 CO 3 in g.

[0040] After 120 min of carbonization reaction, it is obtained that the carbonization rate of the LiHCO 2 solution with a CO 3 flow rate of 1.0 L / min is the highest (see Table 1 and Appendix Figure 2 ).

[0041] Table 1 Carbonization rates at different CO 2 flow rates

[0042]

[0043] 2. Influence of different solid-liquid ratios on carbonization rate

[0044] Weigh 50 g of the crude lithium carbonate prepared from salt lake brine and add it to a three-necked flask; add ultrapure water to the three-necked flask according to the solid-liquid ratios of 1:25, 1:30, 1:35, and 1:40 to obtain a mixed liquid; insert the CO 2 gas and the aeration head of the micro-nano bubble generator into the mixed liquid; under the conditions of a temperature of 25 °C, a stirring speed of 350 rpm / min, a CO 2 flow rate of 1 L / min, a time of 120 min, and a micro-nano bubble generator flow rate of 2.5 L / min, carry out a carbonation reaction to generate a LiHCO 3 solution, and calculate the carbonation rate of the LiHCO 3 solution (the carbonation rate calculation formula is the same as above).

[0045] When the solid-liquid ratio is 1:30 and the carbonation reaction is carried out for 120 min, the highest carbonation rate of the LiHCO 3 solution is obtained (see Table 2 and Appendix Figure 3 for details).

[0046] Table 2 Carbonation rates at different solid-liquid ratios

[0047]

[0048] 3. Influence of different carbonation reaction times on the carbonation rate

[0049] Weigh 50 g of the crude lithium carbonate prepared from salt lake brine and add it to a three-necked flask; add 1500 mL of ultrapure water to the three-necked flask according to the solid-liquid ratio of 1:30 to obtain a mixed liquid; insert the CO 2 gas and the aeration head of the micro-nano bubble generator into the mixed liquid; under the conditions of a temperature of 25 °C, a stirring speed of 350 rpm / min, a CO 2 flow rate of 1 L / min, carbonation times of 30, 60, 90, and 120 min, and a micro-nano bubble generator flow rate of 2.5 L / min, carry out a carbonation reaction to generate a LiHCO 3 solution, and calculate the carbonation rate of the LiHCO 3 solution (the carbonation rate calculation formula is the same as above).

[0050] After the carbonation reaction for 120 min, the highest carbonation rate of the LiHCO 3 solution is obtained (see Table 3 and Appendix Figure 4 for details).

[0051] Table 3 Carbonation rates at different carbonation times

[0052]

[0053] 4. Influence of different carbonation reaction temperatures on the carbonation rate

[0054] Weigh 50 g of the crude lithium carbonate prepared from salt lake brine and add it to a three-necked flask; add 1500 mL of ultrapure water to the three-necked flask according to a solid-liquid ratio of 1:30 to obtain a mixed liquid; insert the CO 2 gas and the aeration head of the micro-nano bubble generator into the mixed liquid; under the conditions of controlling the temperature at 20, 25, 30, 35 °C, the stirring speed at 350 rpm / min, the CO 2 flow rate at 1 L / min, the carbonization time at 120 min, and the flow rate of the micro-nano bubble generator at 2.5 L / min, carry out the carbonization reaction, and the reaction generates LiHCO 3 solution, and calculate the carbonization rate of the LiHCO 3 solution (the carbonization rate calculation formula is the same as above).

[0055] After 120 min of carbonization reaction, when the carbonization reaction temperature is 25 °C, the highest carbonization rate of the LiHCO 3 solution is obtained (see Table 4 and Appendix Figure 5 for details).

[0056] Table 4 Carbonization rates at different carbonization reaction temperatures

[0057]

[0058] 5. Influence of different carbonization reaction stirring speeds on the carbonization rate

[0059] Weigh 50 g of the crude lithium carbonate prepared from salt lake brine and add it to a three-necked flask; add 1500 mL of ultrapure water to the three-necked flask according to a solid-liquid ratio of 1:30 to obtain a mixed liquid; insert the CO 2 gas and the aeration head of the micro-nano bubble generator into the mixed liquid; under the conditions of controlling the temperature at 25 °C, the stirring speeds at 250, 300, 350, 400 rpm / min, the CO 2 flow rate at 1 L / min, the carbonization time at 120 min, and the flow rate of the micro-nano bubble generator at 2.5 L / min, carry out the carbonization reaction, and the reaction generates LiHCO 3 solution, and calculate the carbonization rate of the LiHCO 3 solution (the carbonization rate calculation formula is the same as above).

[0060] After 120 min of carbonization reaction, when the carbonization reaction stirring speed is 350 rpm / min, the highest carbonization rate of the LiHCO 3 solution is obtained (see Table 5 and Appendix Figure 6 for details).

[0061] Table 5 Carbonization rates at different carbonization stirring speeds

[0062]

[0063] Optimization method for resin impurity removal parameters

[0064] 1. Influence of Resin Dosage on Impurity Removal Rate

[0065] Accurately measure 5 portions of 100 mL lithium bicarbonate solution (LiHCO 3 ) that have completed the carbonization reaction into 5 3500 mL conical flasks. Add 0, 5, 10, 15, 20, and 25 g of LS1000 ion exchange resin (1 BV = 450 mL) to them respectively. Control the rotation speed at 250 rpm / min and the temperature at 25 °C, and shake in a constant temperature water bath oscillator. After adsorption for 2 h, take samples to analyze the impurity content and calculate the removal rate (see Table 6 and Figure 7 ).

[0066] After the resin addition amount reaches 15 g, the removal rate increases slowly, that is, the addition amounts of 15, 20, and 25 g are all acceptable.

[0067] Table 6 Influence of Resin Dosage on Impurity Removal Rate

[0068]

[0069]

[0070] Optimization Method for Hydrothermal Evaporation Decomposition Reaction Parameters

[0071] 1. Influence of Hydrothermal Evaporation Decomposition Reaction Temperature on Lithium Carbonate Yield

[0072] After the LiHCO 3 solution removes impurities through the LS1000 ion exchange resin (the ion exchange resin addition amount is 15 g), pour the LiHCO 3 solution after removing impurities into beakers in four equal portions, and then place them in a water bath pot in turn for evaporation decomposition at different temperatures;

[0073] Set the water bath pot temperature to 80, 85, 90, and 95 °C. After the water bath pot temperature reaches the set value, carry out evaporation decomposition at a stirring speed of 400 rpm / min for 90 min to obtain a high-purity lithium carbonate solution. Filter the high-purity lithium carbonate solution while it is hot, recycle the mother liquor, and dry the solid in a vacuum oven at 110 °C for 120 min to obtain a dry high-purity lithium carbonate solid, and calculate the yield of the high-purity lithium carbonate solid (the calculation formula is: yield = mfinal lithium carbonate / minitial lithium carbonate * 100%).

[0074] After 90 min of hydrothermal evaporation decomposition reaction, it is concluded that the lithium carbonate yield is the highest at 90 °C (see Table 7 and attachment Figure 8 ).

[0075] Table 7 Yield of Lithium Carbonate at Different Hydrothermal Evaporation Decomposition Temperatures

[0076]

[0077] 2. Influence of Hydrothermal Evaporation Decomposition Stirring Speed on Lithium Carbonate Yield

[0078] LiHCO 3 After the solution removes impurities through LS1000 ion exchange resin (the addition amount of ion exchange resin is 15 g), the LiHCO 3 solution is poured into a beaker in four equal portions, and then placed in a water bath pot in turn for evaporation decomposition at different temperatures;

[0079] Set the temperature of the water bath pot to 90 °C. After the temperature of the water bath pot reaches the set value, set the stirring speeds to 300, 400, 500, and 600 rpm / min respectively. After 90 minutes of evaporation decomposition, a high-purity lithium carbonate solution is obtained. The high-purity lithium carbonate solution is filtered while it is hot, the mother liquor is recycled, and the solid is dried in a vacuum oven at 110 °C for 120 minutes to obtain a dry high-purity lithium carbonate solid, and calculate the yield of the high-purity lithium carbonate solid (the calculation formula is: yield = m final lithium carbonate / m initial lithium carbonate * 100%).

[0080] After 90 minutes of hydrothermal evaporation decomposition reaction, it is concluded that the lithium carbonate yield is the highest at a stirring speed of 400 rpm / min (see Table 8 and Appendix Figure 9 ).

[0081] Table 8 Yield of Lithium Carbonate at Different Stirring Speeds

[0082]

[0083] Example 2

[0084] A method for preparing high-purity lithium carbonate based on the microbubble-assisted method, specifically including the following steps:

[0085] Step 1, Weigh 100 g of crude lithium carbonate prepared from salt lake brine and add it to a three-necked flask for standby;

[0086] Step 2, Add 3000 mL of ultrapure water to the above three-necked flask according to a solid-liquid ratio of 1:30 to obtain a mixed liquid;

[0087] Step 3, Insert the CO 2 gas (purity ≥ 99.9%) and the aeration head of the micro-nano bubble generator into the mixed liquid;

[0088] Step 4, At a temperature of 25 °C, a stirring speed of 350 rpm / min, and CO 2Under the conditions of a flow rate of 1 L / min, a time of 120 min, and a flow rate of the micro-nano bubble generator of 2.5 L / min, a carbonization reaction is carried out, and LiHCO is generated by the reaction. 3 solution, and the unreacted CO 2 is recycled;

[0089] Step 5, pass the LiHCO 3 solution through an ion exchange resin to remove impurities, and obtain the LiHCO solution after removing impurities. 3 solution, wherein the addition amount of the ion exchange resin is 450 g;

[0090] Step 6, carry out a hydrothermal evaporation decomposition reaction on the LiHCO solution after removing impurities, with a reaction temperature of 90 °C, a stirring speed of 400 rpm / min, and a reaction time of 90 min, and finally obtain a high-purity lithium carbonate solution; 3

[0091] Step 7, carry out hot filtration on the high-purity lithium carbonate solution, recycle the mother liquor, and dry the solid in a vacuum oven at 110 °C for 120 min to obtain a dry high-purity lithium carbonate solid;

[0092] Step 8, wash the dry high-purity lithium carbonate solid, dissolve it by adding ultrapure water according to a solid-liquid ratio of 1:5, and carry out washing at a temperature of 85 °C for 30 min; then carry out hot filtration, recycle the mother liquor, and dry the solid in a vacuum oven at 110 °C for 120 min to obtain 98 g of the final high-purity lithium carbonate, with a yield of 98%, detect and analyze its impurity content, and compare it with crude lithium carbonate (see Table 9 for details).

[0093] Table 9 Analysis and comparison of the content of high-purity lithium carbonate and crude lithium carbonate

[0094]

[0095] According to the index analysis, it meets the Li2CO3-04 standard in YS / T-546-2021 for high-purity lithium carbonate.

[0096] Comparative example

[0097] Implemented according to the method of Example 1, except that the particle size of the final product is different by using micro-nano bubble assistance and the traditional carbonization method (see Table 10 for details).

[0098] Table 10 Comparison of the particle size of the final products of the method of the present invention and the traditional carbonization method

[0099]

[0100]

[0101] ​As can be seen from the above table, the particle size of the final product obtained by introducing the microbubble-assisted carbonization method to prepare high-purity lithium carbonate is lower than that of the traditional carbonization method. This is mainly because the increase in local supersaturation can promote nucleation. The microbubble-assisted method improves local supersaturation, forms reaction microzones, and inhibits crystal growth, thereby reducing the particle size of the product and making it more uniform.

[0102] Example 3

[0103] A method for preparing high-purity lithium carbonate based on the microbubble-assisted method specifically includes the following steps:

[0104] Step 1, Weigh 100 g of crude lithium carbonate prepared from salt lake brine and add it to a container for standby.

[0105] Step 2, Add 3500 mL of ultrapure water to the above container according to a solid-liquid ratio of 1:35 to obtain a mixed liquid.

[0106] Step 3, Insert the CO 2 gas (purity ≥ 99.9%) and the aeration head of the micro-nano bubble generator into the mixed liquid.

[0107] Step 4, Under the conditions of a temperature of 25 °C, a stirring speed of 350 rpm / min, a CO 2 flow rate of 1 L / min, a time of 120 min, and a flow rate of the micro-nano bubble generator of 2.5 L / min, carry out a carbonization reaction to generate a LiHCO 3 solution, and recycle the unreacted CO 2 for reuse.

[0108] Step 5, Pass the LiHCO 3 solution through an ion exchange resin to remove impurities and obtain a LiHCO 3 solution after impurity removal, where the addition amount of the ion exchange resin is 520 g.

[0109] Step 6, Carry out a hydrothermal evaporation decomposition reaction on the LiHCO 3 solution after impurity removal, with a reaction temperature of 90 °C, a stirring speed of 400 rpm / min, and a reaction time of 90 min, and finally obtain a high-purity lithium carbonate solution.

[0110] Step 7, Filter the high-purity lithium carbonate solution while it is hot, recycle the mother liquor, and dry the solid in a vacuum oven at 110 °C for 120 min to obtain a dry high-purity lithium carbonate solid.

[0111] Step 8: Wash the dry high-purity lithium carbonate solid by pulping, dissolve it by adding ultrapure water according to a solid-liquid ratio of 1:10, and pulp it at 85°C for 30 minutes; then filter while it is hot, recycle the mother liquor, and dry the solid in a vacuum oven at 110°C for 120 minutes to obtain 92 g of the final high-purity lithium carbonate with a yield of 92%. Detect and analyze its impurity content and compare it with the crude lithium carbonate (see Table 11 for details).

[0112] Table 11 Analysis and Comparison of the Contents of High-Purity Lithium Carbonate and Crude Lithium Carbonate

[0113]

[0114] According to the index analysis, it meets the Li2CO3-04 standard in YS / T-546-2021 for high-purity lithium carbonate.

[0115] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-purity lithium carbonate based on a microbubble-assisted method, characterized in that: Step 1, weighing a certain amount of crude lithium carbonate prepared from salt lake brine and adding it into a container for later use; Step 2, adding ultrapure water into the above container at a solid-liquid ratio of 1:20-40 to obtain a mixed liquid; Step 3, inserting the aeration head of the CO2 gas and the micro-nano bubble generator into the mixed liquid; Step 4, performing a carbonization reaction at a temperature of 20 to 35° C., a stirring speed of ≥200 rpm / min, a CO2 flow rate of 0.25 to 1.5 L / min, a time of 40 to 150 min, and a micro-nano bubble generator flow rate of 2.5 L / min to generate a LiHCO3 solution, and the unreacted CO2 is recycled and reused; Step 5, removing impurities from the LiHCO3 solution through an ion exchange resin to obtain a LiHCO3 solution after the impurities are removed; Step 6, subjecting the LiHCO3 solution after impurities are removed to a hydrothermal evaporation decomposition reaction, with a reaction temperature of ≥90°C, a stirring speed of ≥400rpm / min, and a reaction time of 60 to 150min, to finally obtain a high-purity lithium carbonate solution; Step 7, filtering the high-purity lithium carbonate solution while hot, recycling the mother liquor, and drying the solid in a vacuum oven at 110° C. for 120 min to obtain a dry high-purity lithium carbonate solid; Step 8, slurry washing the dried high-purity lithium carbonate solid, adding ultrapure water at a solid-liquid ratio of 1:5-15 to dissolve it, and slurry washing for 30 minutes at a temperature of 75-85°C; then filtering while hot, recycling the mother liquor, and drying the solid in a vacuum oven at 110°C for 120 minutes to obtain the final high-purity lithium carbonate, detecting and analyzing its impurity content, and comparing it with the crude lithium carbonate.

2. A method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In the step 1, the container is a three-necked flask or a glass reactor, and the weighed amount of crude lithium carbonate is 50 to 100 g.

3. A method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In the step 2, ultrapure water is added at a solid-liquid ratio of 1:30-40, and the ultrapure water can be replaced by the recovered mother liquor in step 7 or 8.

4. The method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In step 3, the purity of CO2 gas is ≥99.9%.

5. The method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In step 4, during the carbonization reaction, the temperature is 25° C., the stirring speed is 250-400 rpm / min, the CO2 flow rate is 1 L / min, the time is 120 min, and the flow rate of the micro-nano bubble generator is 2.5 L / min.

6. The method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In the step 5, the model of the ion exchange resin is LS1000; the amount of the ion exchange resin added is 450-550 g.

7. The method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In step 6, the hydrothermal evaporation decomposition reaction temperature is 90° C., the stirring speed is 400 rpm / min, and the reaction time is 90 min.

8. The method for preparing high-purity lithium carbonate based on a microbubble-assisted method according to claim 1, characterized in that: In the step 8, ultrapure water is added to dissolve the lithium carbonate according to a solid-liquid ratio of 1:5-10, and the washing is performed at a temperature of 85° C. for 30 minutes; the purity of the final high-purity lithium carbonate is 99.997%.

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