Process for producing lithium carbonate from a lithium-containing solution

Abstract

The proposed invention relates to a process for producing lithium carbonate from a lithium-containing solution, and can be used, inter alia, in the fields of chemistry and metallurgy. What is proposed is a process for producing lithium carbonate from a lithium-containing solution, comprising the steps of: (a) producing technical-grade lithium carbonate from a lithium-containing solution; (b) carbonizing the technical-grade lithium carbonate; (c) decarbonizing the solution produced in step (b) and removing the precipitate from the mother liquor. The mother liquor from step (c) is fed to step (b) to dissolve the technical-grade lithium carbonate. The technical result is that of increasing the end-to-end recovery of lithium, increasing the purity of the end product, producing battery-grade lithium carbonate at a low specific consumption of water, and also increasing the effective working life (extending the service life) of an osmosis membrane.

Description

[0001] METHOD FOR PRODUCING LITHIUM CARBONATE FROM A LITHIUM-CONTAINING SOLUTION Technical field

[0002] The proposed invention relates to a method for producing high-purity lithium carbonate from a lithium-containing solution and can be used in chemical, metallurgical and other fields.

[0003] Prior art

[0004] The production of lithium-ion batteries requires high-purity lithium carbonate, which can be obtained from technical grade lithium carbonate.

[0005] From US patent US6048507, published on 11.04.2000, a method for producing high-purity lithium carbonate is known, which includes bicarbonation (carbonation), including the treatment of an aqueous pulp of lithium carbonate with carbon dioxide at room temperature and above at a pressure of 1 to 20 atm, purification of the resulting solution of lithium hydrogen carbonate on an ion-exchange resin based on aminophosphonic acid and debicarbonation (decarbonation) at a temperature of 60-100°C, filtration, washing and drying of the resulting lithium carbonate precipitate.

[0006] The disadvantages of this method are:

[0007] - high specific water consumption associated with the need to use water to dissolve (bicarbonate) lithium carbonate;

[0008] - relatively high losses of lithium with the debicarbonation mother liquor.

[0009] The closest analog is patent RU2659968, published July 4, 2018, which describes a method for producing lithium concentrate from lithium-bearing natural brines and processing it into lithium chloride or lithium carbonate. In this method, primary lithium concentrate obtained from lithium-bearing natural brine is converted into secondary lithium concentrate as follows. A specified weight amount of PgCO3 is slurried in a solution obtained by reverse osmosis concentration—the desalination of primary lithium concentrate in a stream of reverse osmosis lithium concentrate.The pulp is carbonized with carbon dioxide or a gas mixture containing CO2 in pulp circulation mode until the lithium carbonate is completely dissolved. The solution is heated to a temperature of 80-85°C under vacuum to 0.5 atm. The pulp is decarbonized by directing the released carbon dioxide to the carbonization operation of the pulp prepared from lithium carbonate and reverse osmosis lithium concentrate, and simultaneously converting CaCE and MgCE into insoluble precipitates of CaCO3 and Mg(OH)2-3MgCO3-3H2O, which are separated from the liquid phase. The liquid phase, which is an aqueous solution of LiCl with an admixture of NaCl and KCl, is concentrated for lithium chloride by electrodialysis or thermal means, or a combination of both, to obtain a LiCl solution with a concentration of 190-200 kg / m3. 3 , corresponding to the composition of the secondary lithium concentrate, which is subsequently used to obtain lithium chloride or lithium carbonate.

[0010] The disadvantages of the above-mentioned invention include insufficient lithium recovery, high specific water consumption, and relatively high lithium losses in the decarbonation mother liquor. Additional disadvantages of the above-mentioned invention include the limited service life of the reverse osmosis membranes and the increased costs of their cleaning and regeneration.

[0011] Disclosure of invention

[0012] In this application: mixing (blending) is the addition of one component to another; mother liquor is the liquid phase (liquid) after the separation of the precipitate from it; technical grade lithium carbonate is lithium carbonate containing impurities; purification from impurities is at least partial removal of impurities from the product (solution) being purified. After such a procedure, the product (solution) is considered to be purified from impurities, even if some amount of impurities remains in it; solution is a homogeneous mixture of substances, wherein incomplete dissolution of one substance in another does not exclude the fact that the solution is obtained in relation to that part that is completely dissolved.Thus, a solution containing a precipitate can be in a container simultaneously with an undissolved precipitate, this does not exclude the fact of the presence of a solution and its direction to the appropriate stages; dissolution - obtaining a solution; concentrate - a solution having a lithium concentration higher than the lithium concentration in the solution at the previous technological stage; concentration - a stage at which a solution is obtained having a lithium concentration higher than the lithium concentration in the solution at the previous technological stage; reverse osmosis concentration - concentration using reverse osmosis; carbonation (bicarbonation) stage - a stage including the dissolution of lithium carbonate in the presence of carbon dioxide, resulting in the formation of a solution containing lithium hydrogen carbonate (lithium bicarbonate, NHCO3); decarbonation (debicarbonation) stage - a stage including the precipitation of lithium carbonate, resulting in the formation of a pulp (mixture) containing a precipitate and a mother liquor.

[0013] The objective and technical result of the present invention is to increase the through extraction of lithium, to increase the purity of the resulting product, to obtain battery-grade lithium carbonate with a low specific water consumption, and to increase the effective operating life of osmosis membranes (increase service life).

[0014] To solve the stated problem and achieve the technical result, a method for obtaining lithium carbonate from a lithium-containing solution is proposed, which includes the following stages:

[0015] (a) obtaining technical grade lithium carbonate from a lithium-containing solution;

[0016] (b) carbonation of technical grade lithium carbonate;

[0017] (c) decarbonating the solution obtained in step (b) to separate the precipitate from the mother liquor, wherein the mother liquor from step (c) is fed to step (b) to dissolve technical grade lithium carbonate.

[0018] Using mother liquor instead of pure water significantly reduces the water required for the carbonation of technical lithium carbonate. Reusing the mother liquor increases lithium recovery, reducing lithium losses during the carbonation / decarbonation stage from 20% to 2%.

[0019] In a preferred embodiment, the mother liquor from step (c) is fed to step (b) until the sodium content of the mother liquor is less than or equal to 300 mg / L.

[0020] The use of a mother liquor having a sodium content of less than or equal to 300 mg / l results in an additional increase in the through extraction of lithium and an additional increase in the purity of the resulting product.

[0021] In a preferred embodiment, step (a) comprises step (al) of reverse osmosis concentration of the lithium-containing solution, whereby when the sodium content in the mother liquor from step (c) is more than 300 mg / l, its pH is adjusted to a value in the range of 1.01-3, preferably 2-3, and sent to step (al).

[0022] Directing the mother liquor, having a sodium content greater than 300 mg / l, to the reverse osmosis stage with preliminary acidification of the mother liquor to a pH of 1.01-3, preferably 2-3, makes it possible to eliminate the loss of lithium with the mother liquor, thereby further increasing the extraction of lithium and, thus, further increasing the degree of extraction of lithium, as well as significantly increasing the service life of the osmosis membranes.

[0023] In a preferred embodiment, the supply of mother liquor from stage (c) to stage (b) is carried out in the volume of mother liquor obtained in the first three cycles of the method.

[0024] The use of the mother liquor from the first three cycles of the method, i.e. until the sodium content has exceeded 300 mg / l, leads to an additional increase in the through extraction of lithium and an additional increase in the purity of the resulting product.

[0025] A cycle is defined as a single execution of stages (a), (b), and (c). The cycle can be repeated any number of times.

[0026] In a preferred embodiment, step (a) comprises step (al) of reverse osmosis concentration of the lithium-containing solution, wherein the mother liquor obtained in step (c) in the fifth and subsequent cycles of the method is sent to step (al), wherein its pH is adjusted to a value in the range of 1.01-3, preferably 2-3.

[0027] After the maximum number of cycles, the decarbonation mother liquor is sent to the reverse osmosis stage, with preliminary acidification of the mother liquor to a pH of 1.01–3, preferably 2–3. This technique improves lithium recovery and significantly extends the service life of the reverse osmosis membranes.

[0028] In a preferred embodiment, the pH of the mother liquor is adjusted to the desired value by adding hydrochloric acid. The pH of the mother liquor can be adjusted (adjusted to the desired value) using any method known in the art suitable for this purpose. However, the use of hydrochloric acid is preferred.

[0029] In a preferred embodiment, before stage (c), at least partial sorption purification of the solution obtained in stage (b) from impurities of Ca, Mg, and B is carried out.

[0030] This leads to an additional increase in the purity of the resulting product.

[0031] In a preferred embodiment, step (a) comprises step (al) of reverse osmosis concentration of the lithium-containing solution and step (a2) of precipitation to obtain technical grade lithium carbonate, wherein the precipitate obtained in step (c) is washed with water having a temperature in the range of 80-99°C, preferably 90-95°C, and at least part of the water used for washing is diverted for use in step (a2).

[0032] This results in a further increase in the through-hole lithium recovery.

[0033] In a preferred embodiment, at step (b), the carbon dioxide pressure in the reactor is from 4 to 4.5 atm.

[0034] This mode allows for more complete precipitation of lithium carbonate and thereby further increases lithium extraction.

[0035] In a preferred embodiment, at stage (c) the decarbonization reactor is stirred and heated to 90-95°C, while the solution obtained at stage (b) is kept in the reactor for at least an hour, preferably 3.5-5 hours.

[0036] This mode allows for more complete precipitation of lithium carbonate and thereby further increases lithium extraction.

[0037] In a preferred embodiment, at step (b), the L:S ratio without the participation of the mother liquor from step (c) is from 17 to 22, and the L:S ratio with the participation of the mother liquor from step (c) is from 22 to

[0038] 27. The specified L:S ratio allows for the maximum concentration of lithium to be achieved in the lithium bicarbonate solution (at the solubility limit), resulting in more battery-grade lithium carbonate being produced in one cycle and also allowing for further increase in lithium extraction.

[0039] The liquid:solid ratio is the ratio of the masses of the liquid phase to the solid phase. In ranges specified in the format "from ... to ...," the boundary values ​​are included within the specified range (inclusive).

[0040] Brief description of the drawings

[0041] The drawings are presented for a better understanding of the invention, however, it will be obvious to a person skilled in the art that the disclosed invention is not limited to the embodiment shown in them.

[0042] Fig. 1 shows a block diagram of the circulation (movement) of flows according to the invention.

[0043] Fig. 2 shows a block diagram of the embodiment of the invention in its best form.

[0044] Embodiments of the invention. The best embodiment of the invention.

[0045] The described embodiments of the invention are provided for illustrative purposes only. It will be obvious to those skilled in the art that other embodiments are possible without changing the essence of the invention.

[0046] As shown in Fig. 1, lithium-containing raw material (lithium-containing solution) is fed along line 1a to stage 1 of reverse osmosis concentration.

[0047] From stage 1 of reverse osmosis concentration, the concentrate is taken through line 2a to stage 3 of obtaining technical grade lithium carbonate (technical grade lithium carbonate is lithium carbonate containing impurities).

[0048] Technical grade lithium carbonate is fed via line 3 to stage 3 of technical grade lithium carbonate carbonation.

[0049] From stage 3 of carbonation, technical-grade lithium hydrogen carbonate is fed via line 4a to stage 4 of decarbonation, where battery-grade lithium carbonate is precipitated, the mother liquor is separated from the lithium carbonate precipitate, and the lithium carbonate precipitate is washed.

[0050] Prior to decarbonization, complete or partial sorption purification of Ca, Mg, and B, filtration of mechanical impurities, and other steps known in the art may be performed. The battery-grade lithium carbonate precipitate is then removed from decarbonization unit 4 via line 4b for drying.

[0051] The mother liquor separated from the lithium carbonate precipitate is returned to the previous stages.

[0052] If the sodium content in the mother liquor is less than or equal to 300 mg / l, it is sent via line 3c to the carbonation block 3 to the carbonation stage (dissolution of technical lithium carbonate).

[0053] If the sodium content in the mother liquor is more than 300 mg / l, it is fed through line 5a to tank 5 for neutralization, where the pH of the solution is brought to a value of 1.01 - 3 (preferably to 2-3) by adding concentrated hydrochloric acid, and then sent to block 1 of reverse osmosis concentration.

[0054] As shown in Fig. 2, lithium-containing raw material (lithium-containing solution) is fed through line 1a for concentration (reverse osmosis concentration), and then for lithium carbonate precipitation, from which technical lithium carbonate (technical-grade lithium carbonate, i.e. lithium carbonate containing impurities) is removed.

[0055] Then the technical lithium carbonate is fed to the bicarbonation (carbonation) stage, where carbon dioxide is also fed.

[0056] The main impurities present in technical lithium carbonate are Na, K, Ca, Mg and B.

[0057] A reprecipitation process is used to remove Na and K. The process is based on the dissolution of lithium carbonate in the presence of carbon dioxide (the bicarbonation stage), resulting in the formation of lithium hydrogen carbonate (lithium bicarbonate, L1HCO3):

[0058] L12CO3 + CO2+ H2O = 2LiHCO3

[0059] The solubility of lithium bicarbonate in water is higher than that of lithium carbonate. This allows for the production of lithium-containing solutions from which the remaining impurities (Ca, Mg, and B) can be removed by sorption on selective sorbents.

[0060] The bicarbonation (carbonation) process is carried out in a sealed reactor. Water is added to the reactor, and with stirring, a calculated amount of technical lithium carbonate is added. The amount depends on the desired lithium concentration in the carbonation solution and the moisture content of the technical lithium carbonate. The mass of technical lithium carbonate for carbonation is calculated using the formula: lithium carbonate for carbonation, g; - molar mass of lithium carbonate, g / mol; j - lithium concentration in carbonation solution, g / l; - molar mass of lithium, > moisture content of technical lithium carbonate for carbonation, %; - volume of water for carbonation, l.

[0061] After adding water and lithium carbonate with constant stirring, the reactor is sealed and carbon dioxide is introduced into the reactor until a pressure of 4 atm is reached. The solution is maintained with constant stirring for 1-1.5 hours until an equilibrium pressure of at least 4 atm is reached. The end of the process is determined by the change in reactor pressure as indicated by the pressure gauge. As the pressure decreases, carbon dioxide is continued to be introduced until the process is complete.

[0062] The resulting lithium bicarbonate solution is sent for sorption purification from Ca ions. 2+ , Mg 2+ and in Oz 3 By passing the impurity elements through sequentially connected columns filled with a sorbent selective for these ions. Upon passing through the sorbent, the ions of the impurity elements form strong bonds with the functional groups of the sorbent and are extracted from the solution.

[0063] The lithium carbonate is then fed to the decarbonization stage where lithium carbonate is precipitated.

[0064] Carbon dioxide separated at the decarbonization stage is sent to the bicarbonization stage.

[0065] During the decarbonization stage, the purified lithium bicarbonate solution is fed into a decarbonization reactor, where it is stirred and heated to 90-95°C. Once the temperature reaches 90-95°C, the solution is held for at least an hour. The decarbonization process itself typically begins at 65°C:

[0066] Without stopping the mixing, the resulting hot pulp is sent to filtration, where the hot pulp is dropped onto a Nutsche filter, the sediment is filtered off, and washed with hot distilled water (90-95°C) to remove residual impurities (in particular, soluble K and Na ions).

[0067] Next, the separated battery-grade lithium carbonate precipitate is dried, and the mother liquor (MOTHER LIQUID 1) separated from the precipitate is sent to the bicarbonation stage to dissolve technical-grade lithium carbonate. The wash water obtained after washing (rinsing with hot water) the lithium carbonate precipitate is sent to the lithium carbonate precipitation stage.

[0068] Decarbonization plays a key role in the production of battery-grade lithium carbonate. The completeness of decarbonization determines the yield of the finished product and, consequently, the efficiency of the entire process.

[0069] The carbonization-decarbonization process allows for the dissolution of technical lithium carbonate, purification from residual impurities, and the production of products of the required quality, using virtually no reagents (provided that the carbon dioxide used is recovered).

[0070] During the decarbonization of lithium-containing solutions, a mother liquor is formed containing Li and impurities of Na, K, Ca, Mg, and B.

[0071] The conventional use of water as a reaction medium for dissolving technical lithium carbonate leads to significant water consumption (about 20-25 liters per 1 kg of technical carbonate), a decrease in the yield of battery lithium carbonate due to its solubility in water, and also to the loss of lithium in the mother liquor.

[0072] The proposed method involves using the mother liquor from the decarbonization stage to re-dissolve technical lithium carbonate, which reduces water consumption.

[0073] After 3-4 cycles, when the sodium concentration in the mother liquor reaches more than 300 mg / l, the mother liquor (MOTHER LIQUID 2) is sent for neutralization, where its pH is adjusted to 1.01-3 (preferably to 3) by adding concentrated hydrochloric acid, and then sent for concentration (reverse osmosis concentration) and returned to the lithium carbonate precipitation stage.

[0074] The achievement of the technical result by the proposed method is demonstrated by the following examples, the results of which are given in Tables 1 and 2.

[0075] Example 1 (based on prototype)

[0076] During the carbonation stage, 6.75 kg of technical lithium carbonate (LiiCCL) with a moisture content of 37.2% was mixed with 80 liters of distilled water. This process produced a slurry, into which carbon dioxide (CO2) was added with constant mixing. The process continued until the excess pressure in the system stabilized at 4 atm. The resulting lithium bicarbonate solution was passed through a sorption column with a sorbent to remove alkaline earth metal cations. After removal of impurities, the bicarbonate solution was fed to a decarbonation reactor, where it was maintained at a temperature of 90°C for 4 hours. After this holding time, the resulting slurry was filtered on a Nutsche filter and washed with distilled water to remove residual impurities. The washed lithium carbonate precipitate was dried under vacuum at 180°C.As a result of processing, 3.35 kg of lithium carbonate with a moisture content of less than 0.1% was obtained, the analysis results of which are presented in Table 1.

[0077] Example 2 (according to the invention)

[0078] At the carbonation stage, 5.38 kg of technical-grade Li2CO3 with a moisture content of 37.2% were dissolved in 80 l of the Li2CO3 mother liquor obtained by debicarbonation as described in Example 1. The mother liquor had the following composition (mg / l): Li - 2008; Na - 86.1 (the mother liquor obtained in the first cycle of the method). This process produced a pulp into which carbon dioxide (CO2) was supplied with constant mixing. The process continued until the excess pressure in the system stabilized at 4 atm.

[0079] The resulting lithium bicarbonate solution was passed through a sorption column with a sorbent to remove alkaline earth metal cations. After removal of impurities, the bicarbonate solution was fed to a decarbonization reactor, where it was maintained at 90°C for 4 hours. After this holding time, the resulting slurry was filtered on a Nutsche filter and washed with distilled water to remove residual impurities. The washed lithium carbonate precipitate was dried under vacuum at 180°C. The processing yielded 3.42% lithium carbonate with a moisture content of less than 0.1%. The analytical results are presented in Table 1.

[0080] Example 3 (according to the invention)

[0081] At the carbonation stage, 5.45 kg of technical grade L12CO3 with a moisture content of 37.2% were dissolved in 80 l of the L12CO3 mother liquor obtained as a result of decarbonation according to Example 2. The mother liquor had the following composition (mg / l): Li - 1868; Na - 147.1 (the mother liquor obtained in the second cycle of the method). As a result of this process, a pulp was obtained, into which carbon dioxide (CO2) was supplied with constant mixing. The process continued until the excess pressure in the system stabilized at 4 atm. The resulting lithium bicarbonate solution was passed through a sorption column with a sorbent to purify it from alkaline earth metal cations. After purification from impurities, the bicarbonate solution was fed to the decarbonation reactor, where it was maintained at a temperature of 90 °C for 4 hours. At the end of the aging period, the resulting pulp was filtered on a Nutsche filter and washed with distilled water to remove residual impurities.The washed lithium carbonate precipitate was dried under vacuum at 180°C. Processing yielded 3.47 g of lithium carbonate with a moisture content of less than 0.1%. The analysis results are presented in Table 1.

[0082] Example 4 (according to the invention)

[0083] At the carbonation stage, 5.53 kg of technical-grade Li2CO3 with a moisture content of 37.2% were dissolved in 80 l of the Li2CO3 mother liquor obtained by decarbonation as in Example 3. The mother liquor had the following composition (mg / l): Li - 1708.5; Na - 202.7 (the mother liquor obtained in the third cycle of the method). This process resulted in a pulp into which carbon dioxide (CO2) was supplied with constant mixing. The process continued until the excess pressure in the system stabilized at 4 atm.

[0084] The resulting lithium bicarbonate solution was passed through a sorption column with a sorbent to remove alkaline earth metal cations. After removal of impurities, the bicarbonate solution was fed to a decarbonation reactor, where it was maintained at 90°C for 4 hours. After this holding time, the resulting slurry was filtered on a Nutsche filter and washed with distilled water to remove residual impurities. The washed lithium carbonate precipitate was dried under vacuum at 180°C. The processing yielded 3.42% lithium carbonate with a moisture content of less than 0.1%. The analytical results are presented in Table 1.

[0085] Example 5 (according to the invention)

[0086] At the carbonation stage, 5.64 kg of technical-grade L12CO3 with a moisture content of 37.2% were dissolved in 80 l of the L12CO3 mother liquor obtained through decarbonation according to Example 4. The mother liquor had the following composition (mg / l): Li - 1578.3; Na - 249.6 (the mother liquor obtained in the fourth cycle of the method). This process resulted in a pulp into which carbon dioxide (CO2) was supplied with constant mixing. The process continued until the excess pressure in the system stabilized at 4 atm. The resulting lithium bicarbonate solution was passed through a sorption column with a sorbent to remove alkaline earth metal cations. After purification from impurities, the bicarbonate solution was fed to the decarbonation reactor, where it was maintained at a temperature of 90 °C for 4 hours. At the end of the aging period, the resulting pulp was filtered on a Nutsche filter and washed with distilled water to remove residual impurities.The washed lithium carbonate precipitate was dried under vacuum at 180°C. Processing yielded 3.42 g of lithium carbonate with a moisture content of less than 0.1%. The analysis results are presented in Table 1.

[0087] Example 6 (according to the invention)

[0088] The Li2CO3 mother liquor obtained from decarbonation in Example 4 (the mother liquor obtained in the fourth cycle of the process) was sent for neutralization, where its pH was adjusted to 3 by adding concentrated hydrochloric acid. It was then sent to reverse osmosis concentration and lithium carbonate precipitation. This method further increased the lithium recovery rate and extended the service life of the reverse osmosis membranes by 7%.

[0089] Example 7 (according to the invention)

[0090] The Li2CO3 mother liquor obtained from decarbonation in Example 5 (the mother liquor obtained in the fifth cycle of the process) was sent for neutralization, where its pH was adjusted to 3 by adding concentrated hydrochloric acid. It was then sent to reverse osmosis concentration and lithium carbonate precipitation. This method further increased the lithium recovery rate and extended the service life of the reverse osmosis membranes by 5%.

[0091] Table 1 The test results of the claimed method are presented in Table 2 below.

[0092] Table 2

[0093] Thus, the claimed invention provided:

[0094] - increasing the efficiency of the lithium production process,

[0095] - high extraction of lithium from lithium-containing solutions, production of high-purity lithium carbonate (battery grade lithium carbonate), - reduction of water consumption,

[0096] - increasing the effective operating life of osmosis membranes (increasing service life).

Claims

Invention formula 1. A method for producing lithium carbonate from a lithium-containing solution, comprising the following steps: (a) obtaining technical grade lithium carbonate from a lithium-containing solution; (b) carbonation of technical grade lithium carbonate; (c) decarbonization of the solution obtained in step (b) with separation of the precipitate from the mother liquor, characterized in that the mother liquor from step (c) is fed to step (b) for dissolving technical grade lithium carbonate.

2. The method according to claim 1, characterized in that the mother liquor from step (c) is fed to step (b) until the sodium content in the mother liquor is less than or equal to 300 mg / l.

3. The method according to item 2, characterized in that at step (a) step (al) of reverse osmosis concentration of the lithium-containing solution is carried out, wherein when the sodium content in the mother liquor from step (c) is more than 300 mg / l, its pH is adjusted to a value in the range of 1.01-3, preferably 2-3, and it is sent to step (al).

4. The method according to item 1, characterized in that the supply of the mother liquor from stage (c) to stage (b) is carried out in the volume of the mother liquor obtained in the first three cycles of the method.

5. The method according to item 4, characterized in that at step (a) step (al) of reverse osmosis concentration of the lithium-containing solution is carried out, wherein the mother liquor obtained at step (c) in the fifth and subsequent cycles of the method is sent to step (al), wherein its pH is brought to a value in the range of 1.01-3, preferably 2-3.

6. The method according to item 3 or item 5, characterized in that the pH of the mother liquor is adjusted to a given value by adding hydrochloric acid.

7. The method according to item 1, characterized in that before step (c), at least partial sorption purification of the solution obtained in step (b) is carried out to remove impurities of Ca, Mg, and B.

8. The method according to claim 1, characterized in that in step (a) a step (al) of reverse osmosis concentration of the lithium-containing solution and a step (a2) of precipitation are carried out to obtain technical-grade lithium carbonate, wherein the precipitate obtained in step (c) is washed with water having a temperature in the range of 80-99°C, preferably 90-95°C, and at least part of the water used for washing is diverted for use in step (a2).

9. The method according to item 1, characterized in that at step (b) the pressure of carbon dioxide in the reactor is from 4 to 4.5 atm.

10. The method according to item 1, characterized in that at step (c) the decarbonization reactor is stirred and heated to 90-95°C, and the solution obtained at step (b) is kept in the reactor for at least an hour, preferably 3.5-5 hours.

11. The method according to item 1, characterized in that at stage (b) the L:S ratio without the participation of the mother liquor from stage (c) is from 17 to 22, and the L:S ratio with the participation of the mother liquor from stage (c) is from 22 to

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